I've never had a chance to try either of those. I'd like to know what people think too.
I've been using a BSS box. It does a decent job. I had a Stewart before that and I just wore it out giging. Everyone said get Countryman. I tried it. It was fine, but the BSS sounded every bit as good, and the thing is absolutely indestructible.
If I got an Avalon or something I'd probably never take it out live, but it would be interesting to try it in my studio setup.
I have been using an ol' Whirlwind IMP DI since I started playing bass. A buddy of mine bought it for his electric percussion set-up and gave it to me when he quit. I'ts always served me well, but I may be in the market for a new one-something that's killer for all-around(bass, guitar, keys, etc...). I'm kinda looking at the Countryman as well.