Dan,
I have the fullsacs. Have only heard good things about them. I can see why the Cycle Shack baffles cost less. They have fewer baffles which cost more to cut. The appear to be a hybrid about one half way between stock and fullsac.

1544 PERFORMANCE BAFFLES FOR 4 END CAP MUFFLERS
PERFORMANCE BAFFLES FOR 4" END CAP MUFFLERS: $57.95
Performance Baffles designed to replace the baffles supplied in the 4" O.D. Screamin' Eagle End Cap Muffler kits. WAKE UP those engines with improved power and sound without the obnoxious crackle of straight pipes. Replacement hardware and Torx bit included in kits. Fits the following Part Nos. 64985-07, 64985-07A, 65259-00, 65467-05, 80463-06 and 80464-06. The O.E. BAffles on these mufflers may be retained with 3 spot welds. In order to remove the O.E. baffles these short spot welds must be removed by grinding, being very careful not to grind through the muffler shell and damaging the chrome finish. May need to order CRT-1, baffle removal tool separately. For off-road use only.