It depends on the effort you want to put in, and the tables you want to play.

VPX has the largest table collection, and the good ones play very well. But there is also Pinball FX which is a lot easier to set up, and they are catching up in terms of cabinet support (we're helping them, the next thing is force feedback support).

There is also Future Pinball which runs a few original games with mods pretty well now, but it's still closed source.

You’ll probably end up primarily running Visual Pinball. Some of emulations are nearly perfect if you disregard nudging; I’ve never been able to get convincing nudge physics.

Pinball FX is pretty fun too, but it definitely feels more like a video game than VPX.

Oh, and if you don't know where to start, check this out:

http://mjrnet.org/pinscape/BuildGuideV2/BuildGuide.php

Yes. I don't even bother with anything else on my cab anymore. Good VPX tables are the best looking and best playing and there are a ton of them now with more being made by the community all the time.