It is very much a personal opinion really, though the JVC M90 and Conion 100 are largely revered in the community.
Just remember that one persons' trash is another persons' treasure.
Me, I like the grails above but to me a true grail is one that has been resurrected and put back to glory, a unit that reminds me of the day I did headspins and held by crotch while doing the windmill and competing against other crews all over the country. What I'm trying to say is that a grail is really that unit that makes you tingle when you think about what it meant to you growing up.
Just my 2p.