Yikes!!
I confess I'm a bit of a Luddite when it comes to amps and have an unfair bias towards some amount of genuine valve in the path. My friend bought an M-Pulse 600 on the basis of hearing mine through the Diesel 2x15 that was my cab until about 2 years ago. I bought the two Subway 1x15's to replace the old 2x15. Using the M-Pulse and Subway cabs gives me the same sound as I had with the Bass 400 and Diesel rig IMHO.
My friend tends to use his M-Pulse too, I should add. Just to throw a further spanner, if the weight of the amp ever proved to be prohibitive for me, I would happily use the Subway. The tone was certainly the same (pretty much) across the range of amps but the valve pre-amps did have 'something' which may have just been valve colouration but not to the extent that we thought it was completely different.
I think the vagueness of that answer suggests that we didn't think there was much of any significant difference but I have let my bias towards valves colour my judgement in favour of the M-Pulse.