Based on the above link, the MT3000 should be basically the same size as the Beryl/Slate Plus. That’s still quite a bit bigger than the original Slate, and certainly larger than the WR902AC, but it’s also close to 10x faster on OpenVPN, which seems like an acceptable tradeoff to me. Of course, I’d love something the size of the original AR750, but somehow I don’t think that’s happening any time soon.
For a travel router, the size and weight combined with basically equivalent performance makes the MT3000 much more compelling from my standpoint. At the end of the day both of them are probably going to require a decent USB-C source, so I’m not sure that is a huge selling point between them.
To me, aside from the size/weight, the underlying software support is the biggest differentiator between the two. I certainly would take an MT3000 running a more modern kernel with a chance of real upstream OpenWRT support soon over the current situation on the AXT1800. The loss of the microSD card is a little disappointing, but overall it’s certainly a tradeoff I can live with given the various benefits.