I think 'Titles' has some really cool, weird bass playing, but it tends to be somewhat repetitive. I'd start with 'Bestial Cluster', which is similar to 'The Tooth Mother' but a little more accessible I think. The title song is great! I like 'Dreams of Reason', but definitely not for the bass playing, as it only has bass on like 3 tracks! His newest one, 'More Better Different' is worth checking out as well. It's not great, but it does have some awesome songs. "The Show" and the first two tracks are up there with his best stuff. And it's definitely better than his last album 'Each Eye a Path', which was really slow and depressing and lacking in bass.
The one difference between Karn and Percy Jones (besides their different playing styles of course), is that Karn has put out some good solo albums and he plays on more accessible albums. Jones tends to stick to fusiony stuff, which at times can get a little cheesy. I mean there's no way I'd listen to Brand X if it wasn't for the bass playing. I think he's at his best when he plays in an experimental pop setting. Because he gives the songs so much more punch, and he can let loose with everything he's got for the shorter song length. In fusion tracks, his ideas are more spread out and not as in your face. My favorite work of his is on the album 'Night Mirage' by Ippu-Do. His bass playing pops in and out and is all over the place, adding to the crazy feel of the music. And fretless bass and steel pans is one of the best combos.
I mean, really, would any of us care about a band like Tunnels if it weren't for Percy? I think John Goodsall's guitar is really cheesy and outdated and wanky.