What Is The Best .91 Four Stroke????
Raybo,
The "best" of the two is up to you. Each has pros & cons many of which have been mentioned.
O.S. 91 FS:
Pros:
-relatively short break-in.
-lighter than the TT
-replacement parts may be easier to get a hold of than TT*
Cons:
-more expensive than TT
-not quite as much power as TT
TT 91 FS:
Pros:
-costs less than O.S.
-slightly more power than O.S.
Cons:
-relatively lengthy break-in
-slightly heavier than O.S.
-replacement parts may be more difficult to get a hold of than O.S.*
In a nutshell that is what you're looking at.
Note: comments ending with an * are speculative.