I can tell you from first hand experience, the solid lifter cam will be less prone to valve float at higher RPM (6000+) and will eat up less HP do to less mechanical work needed, make the oil windage problems subside a little too, but for an endurance type application a mechanical type lifter beats the living crap out of everything, think of hydraulic lifters as little shock absorbers, so if your looking for a "set it and forget it" with a solid, IMO I wouldn't go that route.
A hydraulic on the other hand has it's limitations as well, the action of valve float is a "catch 22", yeah it causes problems with valvetrain parts, but at the same time limits engine RPM, keeps from breaking bigger stuff, "Little rev limiters"
Best of both worlds, again IMO, mechanical roller, very expensive, but worth every penny for a bulletproof valvetrain pretty tuff stuff.
I agree with PW, open to way too much debate to be right or wrong, I just hate adjusting valves
Ultimately, the engine needs to be built around the valvetrain, not the other way around, which unfortnately I have screwed up everytime....
