The m1/m2 looks like poweredge r630 equivalent with v3/v4 cpu and m4 is using scalable Xeon which is one generation newer. All of them are great systems, especially when maxed out. The m4 being the newest is probably the best all around choice.
From power point of view, they’re gonna be “less” energy efficient than consumer diy stuff in that they’re supposed to be highly dense systems ran in a data centre with thousands of other similar servers, to pack as much punch in as little space as possible.
Another thing I’d be wary about is noise… 1U means you’re stuck with itty bitty tiny fans that need to spin very quickly and make a lot of noise, should your components heat up. Again, that whole data centre high density thing… noise isn’t something they’re optimizing for.