The .44 Magnum has a relatively high expansion ratio so small decreases in barrel length aren't going to affect muzzle velocity as much as, say, a .357 Magnum which benefits more from longer barrels. So any velocity consideration between the 7.5" or 5.5" barrels is splitting a fine hair.
Both are over 3 pounds, the 5.5 just over and the 7.5 adds another five ounces so neither one is a "packin' gun" kind of gun. That extra 2" of barrel out front does reduce recoil but again, with full power loads in a .44 Magnum both fall into the "it's really gonna kick" category. The extra 2" also adds more sight radius but it sounds like you anticipate shooting at ranges and at targets that don't require that last nth degree of precision.
My personal choice would be a 5.5" just for the slightly reduced weight and the fact that for the purposes indicated you're not handicapping yourself ballistically. If'n it was a dedicated hunting handgun where 100 yard shots might be reasonably expected I'd get the 7.5". Also, this is purely aesthetic but I've had a couple examples of each barrel length over the years and to my mind that 5.5" Redhawk is one of the most balanced looking revolvers out there.
Basically, pay your money and take your pick since either one will fill the bill as well as the other for the purposes indicated.
