With regaqrd to the distributor gears, you can get hydraulic roller cams for FEs that will accept an iron gear on the distributor...so that is an obvious big difference. As I (and Rick) noted, you can try polymer gears on both...Chevy BB guys have used them for a few years, but I'm not sure on long duration tests by anyone with an FE yet. The big advantage (over flat tappets) both offer with longer ramps is a bit wider peak torque range, and better wear. At some point, a flat tappet cam will simply flatten out over time from the pounding...not to mention the chance of doing the same thing when breakin is not performed properly.
The rollers on the tappets (whether solid or hydraulic) simply do away with the pounding...and breakin is essentially a non-issue. I'm not sure one necessarily wears better than the other (presuming the solid roller cam valve adjustment is maintained properly). But that's the thing...less maintenance with the hydraulic roller cam (as with any hydraulic cam...little or no adjustment). The solid roller (like a flat tappet) will run at higher rpms (although that margin of difference has been decreased to where it means little) than the hydraulic version. Not sure that's a big consideration with a BB FE.
Keith has been doing wonderous things with hydraulic roller cams in FEs...probably the hot setup for the street where easy maintenance is desired.
One thing about roller lifters...they need
oil. You've introduced needle bearings into the mix. Shouldn't let them idle at a steady rpm too much...they need splash. Some lifters have better oiling built in versus others. I can tell you from experience that if and when one of those little basturd needle bearings lets go, the remains of the roller lifter become a forked cutting tool on that asspensive roller cam. I'm pretty sure they could cut diamonds in Amsterdam with those things.
Then again, hard to fault the original flat tappet setups...fewer moving parts (the lifters). I've become a strict devotee of KISS with this tin can, and so far it has proven itself to be the way towards nirvanna, universal peace and orgasmic pleasure.