The difference in the velocity really is not that significant ... I have 4", 6", 7.5", and a scoped 9". There is about 250 fps difference between them, at most, depending on powder.
They are all quite accurate. The 7.5" and 9" guns are the most manageable for me, in the recoil department, which is where the difference really lies ... the 4" and 6" have pretty significant muzzle flip.
I like them all. And all of them except the 9" gun carries just as easily in the FA chest holsters that I prefer. If I had to choose just one, would likely go with the 7.5" for versatility.