The 3 barrel lengths listed for the 608 on the Taurus website are:
4"
6 1/2"
8 3/8"
Of these, I would avoid the 8"+ version like the plague, for the reasons stated previously. This thing is a ridiculously bloated, pig of a gun. I think shooting it would get really old really fast!
Get the 6.5" if you must, but I would also personnally stay away from this one as well. The only 608 I would consider is the 4". I handled a blued model once, and it balanced fairly well in my hand, though not as good as my 4" 686. I owned a Taurus 66 6" with the full underlug barrel for a brief time. Good gun, but after a while I began to dislike the way it balanced. It was waaaaay too barrel heavy and it proved difficult to make rapid, accurate shots. I also found that 6" of barrel made for a rather bulky night stand gun.
In fact, I don't like full lug barrels in anything longer than 4". 4" or less, I like both full, half, and no lug barrels. In a 6" gun, I'd keep my eyes open for some sort of
used S&W K Frame. I saw a gorgeous 6" S&W 14-4 recently, and it felt GREAT in my hands, really nice balance. I say used because S&W no longer makes a 6" half lug barrel, .357 Mag
. Morons. As an aside, I wish they'd offer the L Frame 620 (half lug) in a 6" version instead of just the 4". A 5" half lug 686 would be nice to as suggested, but I think they are fairly rare.
Anyway, I think you would find a 6" K balances a lot better and will be more fun to shoot than a big, bloated 608 6.5" Perhaps you could find a range that rents one?