I'd select the 7 1/2" version for small game hunting, if I was selecting a Freedom Arms revolver. In fact I did, and I use that length in both a 97 and an 83/252. I say that, having owned a 9 1/2" Single-Six since 1973. The 7 1/2" is more portable and has adequate sight radius for me.
Now, if you were an avid silhouette shooter, and wanted to use the gun for that purpose also, the 9 1/2- 10" versions would be preferable, for the extra sight radius and to keep the muzzle in front of your leg in Creedmore. I used 10 1/2" SBH's for years in Standing and freestyle Revolver classes, and they were definitely superior to shorter barrels. Of course, you have 30 seconds to load and 2 minutes to shoot 5 shots. Squirrels are much less accommodating.
With regard to 7 1/2" barrel Single-Sixes, a very few were made in 1973-74, and they are very very rare. In the last few years, the Hunter Single-Sixes in .17 and .22 were also offered with 7 1/2" barrels, but you'd better look for them soon, because I understand they've been discontinued.
As an aside, the Ruger T678's are also great squirrel and rabbit guns if semi-autos are legal for hunting where you live.