All the bows I have had up until recently have been 50/60. I just got another Vectrix XL in 60/70, which was too good of a deal to pass up. Both of these bows are set up identically, with the same cams and the same string. The XL 50/60, maxed out at 60 lbs, is pushing a 447 grain arrow at 257 fps. The newer XL 60/70, turned down to 62 lbs, is pushing the same arrow at 260 fps. Cranked up to 72 lbs (max), the newer Vextrix XL will produce 279.5 fps with that same arrow.

So it looks like, at least in the Vectrix XL bows, there is virtually no difference between a 50/60 turned up to 60 and a 60/70 turned down to 60. And, as you go upin draw weight, the speed goes up at the rate of about 2 fps per pound of draw weight.

And, from a practical standpoint, the KE produced by the 60 lb. bow is more than adequate for any North American hunting situation.