Martín Méndez & Chris Squire. One hell of a round, both were tough choices.
I prefer Méndez because his style of bass playing is the type I like, fills up space, adds tasteful touches to the material, and doesn't simply mirror what the guitars are doing. I do think Myung is underutilized in Dream Theater, but I have to go with what they've done as opposed to what they could've done. It's a shame that Myung hasn't ventured into other projects where he could stand out more.
Squire also benefits from a similar case, the music of Yes enabled him to display his capabilities to a greater extent than The Who's music enabled Entwistle to do so. That being said, Squire's ability to carry a tune has very little competition in rock music and his number of memorable basslines is quite high. Entwistle is a worthy competitor though, his punchy fingerstyle playing was a great advance in making the bass a more punchy instrument.