Well... the size thing would be a big differentiator. I picked up a 32G N5X on the Fi deal a bit ago to have the phone as a backup to my 6P (maybe I'll sell it, not sure at this point) and I find it to be quite a capable little phone. Recent updates have really smoothed out the rough edges that existed on launch and now its a nimble little phone. In the time I used it, I was fairly impressed with it and I would have no qualms about recommending it to someone.
Of course, I have not tried a MXPE so I can't say much about it. My reservations with it come solely from my questions about how Lenovo is abusing the Motorola brand... I think it's a shame how they've gutted the Moto team. Most everything that made the Moto line great is no longer with the company... and I fear that the now legacy Moto lineup of phones are going to get cast aside far quicker than they should.