Low UDP speed

We have 2 offices in 2 countries. I try to make a VPN between them. Router 1 - RB1100AHx2, Router 2 - RB1000. Tested tunnels - PPTP, L2TP, OVPN. Internet in both offices is 100Mbps. But then i test with MT Bandwidth test i have in TCP mode about 60 - 80 Mbps, and only up to 10Mbps in UDP mode. Why ? Can someone explain me why this happening ? May be some misconfiguration ?
Thank You in advance !

Test of UDP bandwidth between external addresses shows me 97Mbps in receive or send mode. (!!!). Guys from Mikrotik, can you explain me this LOW UDP BANDWIDTH IN VPN (PPTP, L2TP, OVPN) MODE ??? Please …