I had the blue tube. Neat little unit. A bit dark sounding. I was looking for something more "accurate" or with some sparkle/clarity as my acoustic is pretty dark sounding as it is. So I returned it for an Audio Buddy. I'm happy with the audio buddy. I'd like to jump up a tier to the better quality M-Audio pre after awhile.
In my short little experience with low cost pre's, they can have a world of or subtle differences. I had a soundcard with a built-in phantom powered mic pre. Noisy as hell and not very inspiring (though usable I guess). The little Behr' Eurorack was clean but the unit itself was hella noisy too. As I mentioned, the blue tube is a little dark sounding to me. Others might describe it as warm, others as muddy. A single track recorded with the blue tube may sound great, but once you add other tracks, the muddiness may proof to be problematic (well, in my case at least). I went with the Buddy because of the clarity, and I find it rather sweet sounding, not at all tinny or sharp.