I am closely watching XP progress. Yesterday they released  XP 10.20. with 64 Bit.  I have only XP Demo.
I wonder will CS develop any airplane for XP?
If you have XP, How do you rate them comparison to FSX?

Clarifications. You can't tell, from the looks, if a game runs on OpenGL or DirectX. Example video. http://www.youtube.com/watch?v=HC3JGG6xHN8 So when X-Plane looks different to FSX this doesn't arise from the API in use but mostly from the different artwork and approach made by the developers, not being the ACES team. Here's a XP dev on the details. http://developer.x-plane.com/2009/11/directx-opengl-and-x-plane/

You can surely compare every sim with another one. And that's what we do.   Ahmet's question on the now current XP 10.20 x64 build is a good one. It offers, after a beta phase, a 64 environment and therefore allows some limitations to fade out. Means that situations like 'Your computer has run out of available memory' can still happen, but not at the nowadays low limits like with FSX and P3D. Now this isn't a problem when running the sim at low settings or without a combination of dense and highly detailed addons of course. But the other way around it will become a problem when you are not limited by achievable fps but, later, by a sim running out of usable memory. Combine nice airliner addons and a lot of scenery and you may well see the dreaded 'oom' message. Bummer!

My personal experience with X-Plane is rather positive although it features some downsides like lack of seasonal textures and the huge quality spread among the default planes. Some are very nice and interesting, some others are coming from way older versions of the sim and lack of optics and 'real' feel. Same as with FSX nowadays, it's recommended to get a decent freeware or payware plane to check if the characteristics suit you.
I'd say that the flight model in XP might allow for a more lively feel and also seems to offer a bit of detail when it comes to weather influences. That's different than the FSX feel (mostly with small planes) where you either fly on rails or get totally thrown around because the turbulence got wonky. Best would be somewhere in the middle, right? Well, as said, this all still depends on how much work the plane dev has put into the flight model details. So there are bad planes in XP, same as there are in FSX.

A general advantage of one sim over the other isn't present in my eyes. You can render fairly good planes with the table based approach of FSX and you can also achieve this with the blade element tech of XP. I could see an advantage for XP when leaving the normal flight envelope. So, for smaller planes and some artistic targets, this could come in handy. With airliners, it may not matter a bit or even form up a downside.

Graphics? Well, if you run a modern graphics card in XP, you will benefit a lot. The more the merrier. Means native HDR and a pretty high GPU usage can come together. The CPU isn't used that much. Older ones may still be fine. Also, the nights in XP are just amazing. As a tip, the cloud detail is a major factor in XP. Small cards will need low settings in heavy weather while you can crank that one up with e.g. a GTX680.

Downsides. In a default XP, certainly the ATC and the AI traffic. That stuff is weird.  

Menus, tweaking and calibration. Well, the menus look different, but since the average FSX/P3D user already is a tweak and fiddle guy by design  , they shouldn't cause too much confusion. I did not have to tweak a single cfg file yet and I got my joystick, pedals and throttle running in a few minutes. Same for TrackIR.

The default scenery offers some highlights on the autogen (if one can call it like that) and the roads and villages look a bit more alive. Sort of like zooming in on Sim City if you like. I would love to see more variations though and I also think that the 'smart' road placements overshoots at times. Well, it's default and I'm comparing it to my addon loaded FSX, so keep that in mind.

Stability. I have yet to see any trouble with XP. The fps can be tuned with the default menus and the rest like the resource management is automated. So I never saw memory trouble so far although I did get some of the new '64bit recommended' addons.

So what would be the best way to test? I'd say you should grab the current demo (it should update itself via the tools to 10.20, check that!) and perhaps test some of the default planes and the demo scenery around Seattle. Crank up the details, add clouds and fly at night. The latter is the best part and if you have enabled the road traffic, it will be great.
I think that you can add planes to the demo. So perhaps surf to some freeware sites and look for the comments about a decent flight model. You may then adjust the control sliders in XP to achieve the feel you want. Remember that you may have learned some things the wrong way from FSX. Habits. Not too uncommon among us 'old' sim folks   and we may easily trick ourselves into thinking that wrong is right, if you know what I mean. Just referring to the known FSX flight model downsides we may have gotten used to.

I wouldn't be surprised if the first XP impression is not good. The thing had to grow on me and from being a FSX 'adjusted' fellow, this seems logical at first. So give it some time and keep in mind that supporting those folks gives money to a small company still keeping the flight sim spirit alive against all odds and with really new instead of rewarmed stuff.  

asanal wrote on Mar 9^th, 2013 at 2:48am:

Good observation. What you are seeing is the effect of the clouded skies which may be a bit overstressed in XP. If you set up a low or non existent cloud cover, you can spot the difference. Well, XP even gives you cloud shadows, so that's where some nice detail comes in. We don't know cloud shadows or the altered lighting from FSX/P3D as it's not available (shadows) or just very weak (altered light). Talking about getting used to the wrongness, so to speak. Well, the whole lighting in XP seems very advanced when compared and those night flights are really amazing when coming from the too lit or too dark FSX/P3D world.

On the screen changes, as you call them, you may again be used to the FSX system. As said, those habits may actually block the experience since, when looking closer, pressing S and A isn't too logical either. Well, you can define your keys in XP. I actually have the outside view mapped to S, just because of those nasty FSX habits of mine.  

As for great planes, they are available as far as I can tell. There's a decent 777, another company/McPhat did some nice ATR and you can get a very good CRJ when it comes to airliners. Examples. The prices are comparable or even lower. Freeware may be less detailed but still a lot better than the default XP planes which, as said, aren't always a good starting point although I think the 747 is good for a default plane. Some folks are working on a 737 Classic (that's the -300 to -500 range) payware which looks very good. For obvious reasons, I can't post links here. So the good stuff is available and does compare to the FSX/P3D addons although you may not know the 'new' dev names yet.

Good point on the REX addon. They have done a release for XP9 but I'm looking for the XP10 addon of course. The artwork in XP does not look too promising at times, so my guess would be that REX could help a lot. I find the default XP world a bit too clean. Well, default FSX then is a desert (Eastern Europe, Russia, Asia, even Australia and NZ), so you can pick your favourite.   A tip, there's some great freeware out for NZ which also needs the 64bit version of XP due to the large memory demands.

Yes, I've got the full version since I thought that it could be a nice second sim. With FSX being the main one and showing its age, it can't hurt to support the companies setting up some new stuff. Since bringing the sim to 64bits and already making use of the GPU, it's safe to say that the sim engine is miles ahead of any current FSX/P3D release, still struggling with the huge CPU dependency and memory limits (when running a lot of addons). It wasn't more expensive than a new FSX plus the Acceleration addon and that 'Global' edition also included some addon airports.