How much lift with stock magnum roller lifters?

Stupid question, be gentle...

What the aversion to hydraulic versus solid? Under pressure, the oil is damn near solid and doesn't compress right? I mean, I know it bleeds down but that fast?

I guess I think of it like the experiement kids do with corn starch and water. Add just enough water to a bowl of corn starch to saturate it, then poke your finger in. Goes right down to the bottom. now punch it, and it stops your hand acting like a "solid". In my head it seams similar in that the harder and faster you "hit" the oil, it's going to resist because of the viscosity?

BTW, with all of the talk I see about people wanting solid over hyd, I know I'm 100% wrong, but why?