One is "rated" by Hitec to handle 2S Lipo directly, but we all know that the 7955 is beast as well and can handle it with no issues, but yes @ 6v you are correct they are almost the same servo.

IMO its just up to you which one you want at this point. One saves you money they both are beast and one has even more speed and torque @ 7.4v (7950).

Really up to you. Either way you won't be disappointed with your purchase.