I think it is great that CS is making the 767-300.  I look forward to having this new version.
The other is an excellent sim and will always have its place, but is visually a little outdated compared to some of the newer sims out there and compared to Captain Sim's 757 package.
Captain Sim has perfected the 757 with the release of 4.3 and can now easily expand this quality to the 767, which is only fitting since the maker of the previous 767 is claiming to be working on a 757.

I will definately own Captain Sim's 767 as soon as it hits the shelf (which looks like it may be tomorrow according to the website, I hope).

I would love to see Captain Sim release a kick butt 777 and remake his beautiful Legendary 707 for FSX.  I believe these would prove to be "must haves" by every airline lover, but this 767-300 is a logical choice and will also prove to be a big seller with us Captain Sim fans.