I have no experience with the Force.28....but I have used many Macstar.28 and Hyper.21...they are essentially the same engine but with a different bore....same carb/crank/rod/bearings/head/gudgeon pin/etc.

The Hyper.21 has a few more rpm at the top and the Macstar.28 has a little more torque down low...as expected.
They are both pretty good RTR engines and if I could only choose one then I would have a hard time deciding which to go for...they are very similar in performance terms.

As already said you can gear the larger engine differently to account for the torque/rpm differences between small and large engines...but in my experience there is not a great deal of difference with these two particular engines.