I've never shot PowerBelts, but I have read complaints that they fragment when too much powder is used and the shot is at close range, like less than 50 yds.
FPBs have given me reliable performance on deer from 35-40 to 100 yds.
Full-bore bullets are generally heavier, because they need to be longer in relation to their width for good BC, than a saboted bullet. I recommended the 300 FPB over the 350 simply because you want to shoot longer ranges.
If you can get the 300 gr FPB moving at 2000 fps, which should be achievable with a powder like BH 209, your trajectory will be +2.4" at 50, +3.8 at 100, +2.1 at 150 and -3.1 at 200. Retained energy at 200 will be 1355 ft-lbs. This is from Hornady's ballistic calculator at
http://www.hornady.com/ballistics-re...ics-calculator
I see on the BH site, that 300 gr bullets seem to require a max load of 120 gr to get moving at 2000 fps. 110 gr should get you around 1925 fps.