Awww damn...
I'd have to go with Spock's Beard. As much as I love both Testimony albums and One, the majority of Neal's solo stuff doesn't hold a candle to Spock's Beard, with AND without Neal.
This is a fitting match-up, though, and I would enjoy bringing this topic back up by the end of the fall season when both Neal Morse and Spock's Beard will have released new albums - Morse's Momentum and SBv3's new album, the band's 11th total, with Jimmy Keegan and Ted Leonard as full-time members. The snippets that I've heard of SB11 sound great, and I'm very excited for it, but the prospect of Neal's "World Without End", the near 34-minute epic, sound promising. Ironically, both albums will feature a new part in the "Thoughts" series of songs!
I love Neal Morse's writing and his solo albums, but even while I love them, I can acknowledge that they do tend to sound a lot like each other, whereas SB, after Neal left, did change/evolve/progress into a different sound/identity, while still having that signature that Ryo/Nick/Al/Dave all had when Neal was still in the band. It was still definitively Spock's Beard, and I appreciate their direction and change. Neal has tread a lot of the same ground, but many of his changes, album-to-album, are just to the lyrical content, which does offer some great moments, especially on One and ?, but it does become easy to spot the musical similarities across his body of work.
-Marc.