If you're lookng for more power amp distortion go with the 2:50. The 2:90 is so loud you don't really need to turn it up all that much. The 2:90 also weighs a ton! However, it is designed to switch modes via midi with the Triaxis. Lastly, if you like el34's, I believe there is a bias switch on the 2:50. Although, I've heard you can use el34's in the class A sockets of the 2:90. I hope this helps.