> Is it better to have 2 internet uplinks that 1 internet uplink and 1 of MPLS?   I tend to go for two Internet circuits ... ... View more

I think as soon as you configure  them as a HA mode, one will be a Primary, and the other a Spare which means one is a master, and the other is "ready".         I'm not sure if it will  ever work, but you want to create two networks,  for each MX250 and advertise two different subnets sourcing from each network.     ... View more