For virtual I vote Funhouse. Good flow, fun toys, and Rudy endlessly cracks me up. Love the whole concept. I've played it so many times on PBA, Zen, and VPX; and I can't get sick of it.
But, whenever I see one in real life it's broken in some way. Rudy is slack-jawed, my ball gets stuck unless I tilt the machine, or some component flies off. These plays are all at pinball parlors and museums (passionate operators are running the place). Seems like a real pill to upkeep.
I don't know if I've ever gotten "Frenzy" on the real machine. Last time I played (~2 months ago) my 3rd ball got stuck right before I had a chance to make the shot.
I can't pick a favorite real machine, but the Gottlieb EMs always suck me in.