To add onto what mark said, all the default hotkeys that were present in FSX exist in P3D. Like idle throttle is F1, full flaps F8, etc.   Really helpful when making the switch. Definitely get the academic version. It does everything the professional does. The only difference is the watermark and you dont even notice it when you get busy doing everything. You have completely the wrong impression of P3D. Its basically a 64bit version of fsx. Just much much better. I made the switch and havent regretted it. Depending on your settings and PC, the framerate can drop especially with a lot of PBR and dynamic lighting. Take the settings down a little and you'll be fine. The framerate only drops for me in airports like flytampa's Las Vegas or the new o'hare from fsdreamteam. But I have a gaming laptop. The load times can be abysmal too. Least for me. Usually takes me about 20 minutes to fully load a flight. Might want to prepare for that if you're planning on using complex sceneries or aircraft. It does everything FSX does. As mark said, it's based on fsx. It does take some getting used to though. The UI is different than fsx. I got confused at first. You get used to it though. If nothing else, you will NEVER run out of memory. 64bit programms memory limit is so high, nothing can realistically reach it. That's why P3Dv4 is so good. It no longer has the 4GB memory limit. So if you got OOM(out of memory) errors on fsx, you will never have them again on P3Dv4. It's much more stable. I've not had a single crash since I switched.
One warning though: almost all aircraft addons not updated for P3Dv4 will not work. The only ones that do are ones that use xml for gauges. If the aircraft uses .gau files, it wont work. Quite a few fsx sceneries do work with P3Dv4 though. Off the top of my head cielosim Jacksonville works with a patch from inibuilds, sunskyjet philly works perfectly. Also if you used AES in fsx, it wont work either. GSX Level 2 is far superior anyway. There are a lot of incompatibilities, but alot of devs, CS included, wont make FSX addons anymore.

TLDR: its basically the same thing as FSX. Just some incompatibilities and a different UI. I completely suggest it. Just get the academic version.