Torb's OP unfortunately and strangely doesn't even raise the most crucial problem with Pestosis. CC. Good thing the second post mentions it. This reason alone makes Pestal better, hands down. Something slightly relevant... wizel and I are fighting with Pestal vs. Pestosis in War right now. I won one duel, but the servers went down.
Either way, my experience tells me the denial is usually stronger with Pestal due to the sheer number of Pests in a short time. Against decks where early and little denial is best, Pestosis is faster. When that's not important, Pestal is a lot more stable due to not succumbing to CC and getting out more Pests in a short timespan.
It's worth noting two things about Pestosis though. Upped, it gets the early denial going very fast, which can shut down any bad pillar draw from the opponent. Secondly, it doesn't need as many quanta sources, which means it can pack more utility cards such as Dusk Mantle and CC. On the flip side, this means it's usually easier to deny a Pestosis of quanta in return, because it has less quanta sources.
I vote for Pestal, because it's just not as vulnerable to control.
