The 30M is simply amazing. When I finished this Full Mechanical Overhaul I marveled at the mechanics for days. It is truly beautiful. It plays with all the power of its less ornate sibling, the 10M, and its low production numbers make it rare enough to endow its engineering marvels with even more awe inspiring power.
And if given the choice, I'd take a 10M any day. Simply put, the feel of the key work layout of the 10M is significantly better than the 30M; which is very interesting because the differences in the key work layout are also very subtle.
Aside from all the extra adjustment screws, they look almost identical. But they feel quite different. The 30M is more compact in some regards, especially the lower stack and its relationship to the Eb/C assembly.
But my biggest gripe with the 30M is the reach required to get to the low Bb spatula.
It's enough for my relatively small hands that half the time my LH first finger slips down the B key pearl enough to release its seal on its tone hole. Toggle back and forth between these two photos to see what I'm talking about.
Although I can manage it because I have been playing the saxophone for 25 years and repairing them here in Seattle for 12, I'd rather play a 10M, but I'd also want a 30M, just to look at it.