What makes you doubt the fact that Meraki should not hold up as well as Cradlepoint?
I'm not saying you should mount it under the bus but when you place it inside it should hold out just as well.
The only "challenge" would be the receiver you're purchasing for the MX (or even Z3?) device.
Cradlepoint has a wide support of antennas for receiving 3G/4G/...
It's their core business, so the only thing i could think of is that the reception of mobile networks might work slightly better on Cradlepoint vs Meraki but even that's a guess..
I'm also not sure why you would need 250MBps when working on mobile networks, bandwith of 100Mbps should do and in this case you could consider a Meraki Z3 device.