Can't speak to the sonic differences between the two models, Thomas, but I can tell you that I recently acquired the ML2s to replace my Audiopax 88s, running a pair of Avantgarde Duos. The differences are profound, but not in the hi-fi 'spectacular' way. I always thought that the Audiopax was quite transparent and musical in the mids- and it is- but the Lamm brings a sort of 'relaxed continuousness' to the sound that makes the Audiopax sound forced and almost mechanical by comparison.
The bass- and mind you - the way the Avantgarde is set up I run the Lamms directly to the midhorn with a jumper to the woofer-- is substantially deeper. There is more 'air' around the bass notes, and they sound more like the rest of the range, since I have not been as happy as some with the integration of woofer and horns. NOw, far better.
Also, changing the power cords to the Kubala EMotion, from the Shunyata Anaconda made a real difference too.
If you buy the Lamms, get yourself a high quality meter to check tube bias.
Also, I finally got the correct sized amp stands for the Lamms- I am partial to the Grand Prix Monaco stuff- but experimentation here could pay off too.