Man, I think this is a super tough choice! I'd never played a US MTD until two weeks ago. I actually played #37, a 535-21. It had a swamp ash body, wenge neck/fretboard, original Bartolini pups and electronics......it was a BEAST. Really thick and syrupy tone with no dead spots anywhere on the fretboard. Build was super solid, even after all those years (#37 was built in the 90's I believe, I don't remember the exact date on the neck).
That being said, Smiths are among the first, and most unique sounding boutique instruments. Like above, you always know a Smith when you hear one, doesn't matter the genre of music. A particular album comes to mind that really exhibits that sound to me, well two really....Hezekiah Walker's Live at Morehouse College - Reggie Young on bass (remember "I Will Go in Jesus' Name?" - dat's my JAM lol) and Purpose by Design- Fred Hammond on bass. I personally love the fingerstyle and slap tone, though as you can see the slap sound is pretty polarizing...either you like it or you don't.
Basically, you're comparing apples to oranges. I'll go out on a limb and say you may find the MTD to be a bit more versatile....Smiths will ALWAYS sound like a Smith. Its a great position to be in, and you'd be happy with either bass I think.