this is a very subjective topic that has been discussed hundreds of times...
my personal opinion and taste goes for the 2channels. the older the better. the 3channels have much more versatility due to the pushed and raw modes, and obviously three channels. However their tone is very unclear to my ears. the opposite is true if you are talking about the clean tones. the newer rectos have the best cleans out of all of them. The older 2channels have rather weak cleans, but their distortion is top notch. Others here may agree or disagree. I've owned both models and will be selling my 3ch very soon. good luck!
I have not played a 2 channel yet, but I love the versatility of the 3 channel. It offers much more!
Really depends what you're looking for. If you're going to add pedals to the 2 channel for added versatility, you'll be losing tone there, so each has its drawnbacks.
Prefer the two channel amps including the mark series. I just like simplicity. Don't like have to get rocket science degree to operate a guitar amplifier.