What happens if the box goes down???
What happens if the radios go down, or the servers? Same result... Life sucks... Truck roll.
For me it depends. If it's for a simple access to something, I use PPTP only because it has a native windows client. For the real tunnels I use L2TP with IPSec (Which yes can be a royal bitch to get the hang of, but not bad once you do). I've avoided OpenVPN only because it seems to be even MORE of a bitch to set up than IPSec.
MT is great for setting up tunnels, for business clients that want a transparent L2 tunnel between two locations on our grid, that's where two RB-450G boards, and EoIP/L2TP/IPSec comes into play. By the end of it it's nothing more than a glorified Ethernet cable.