I don't think that either of those two amps sounds better than the other, it's just the question if you want a very transparent hifi sound with lots of highs or if you want a tight and powerful sound. It sounds a little bit compressed compared to the SR Techs (and I'm not talking about the built-in compressor). It doesn't deliver all the high frequencies the SR Techs delivers.
This is a electric bass amp, but from the mentioned electric bass amps, it was certainly the one with the most linear and transparent sound, yet not as linear and transparent as the SR Tech amps. The last combo I tested was the AER Bass One. The sound is as great as the little brother, only more powerful. The SR Tech Jam BB 300 is basically a bigger version of the Jam BB 150 especially designed for double basses, cellos and fretless basses. A nicely defined sound with beautiful lows, transparent mids and tickling highs (or so).
Unlike most bass amps, you get all frequencies your instrument delivers. I didn't like the Schertler Unico very much, but the Jam BB 150 was just great. The Jam BB 150 is not intended to be a bass amp, it rather is an active box with 8" speaker and 6 channel mixer (look here. Next I compared the Schertler Unico and the SR Tech Jam BB 150. Somehow, the filters don't change the sound very much (they work well with electric bass). The downside with this amp is the missing EQ.
The Mark Bass Minimark had no problems with the low E and had overall a more defined and likeable sound. Only the low E was a little bit weak, but still with that, the combo delivers a usable sound. I liked the 8 inch version more as it was less muddy, more transparent. The Genz Benz combos are neat combos and certainly unbeatable for size and weight. First of all, I have to say that all of the mentioned amps delivered a better sound than the GK. The amp I owned before was the Gallien Krueger MB150E-III. I have a 90 year old massive bass and use the vektor pickup (built-in version).