I had the M10/45 first. In stock form it's a bullet-hose built like a brick. Add a solid stock and a suppressor, and it becomes manageable. Switch to 9mm to drop the ROF, and it becomes pretty controllable.
But I eventually sold the M10. But at the time I figured anything it would do, the Uzi I had since acquired could do as well.
Having said that, I have still kept an M11/9 around, and it gets about equal range time as the Uzi. Before Lage started producing his slow-fire uppers, I had drilled my receiver and was doing the TASK slow-fire conversion. I now have a couple of Lage uppers that I use. As noted by others, there seem to be more options for the M11/9 than anything else.
If you primarily intend to run drums with a MAX-31, I would look at the shorter overall package you can get from the MAC11 or M11/380. For a while there, they could be had at a discount to the M11/9, but they seem to be about even any more.
In the end, I'd recommend you keep your eyes open, and try to shoot as many configurations as possible before buying (which admitedly can be difficult, if you don't already know someone with the guns).
With the cost of the MAC series continuing to climb, I might look at a few alternatives if I was shopping for a subgun now. The guns from BRP look interesting, but I haven't played with any. And I've seen some good prices on S&W76 and MK-760 guns in recent months.
