What issues do you have ?
the MR2 P8 is very stable.
if you need a stable firmware then go with MR2 P8.
If you think MR3 P2 will solve your SSLVPN problems then go with that, just remember its not as stable as the MR2, you could get other issues.
FortiGate 200A/B, 224B, 110C, 100A/D, 80C/CM/Voice, 60B/C/CX/D, 50B, 40C, 30B
FortiAnalyzer 100B, 100C
FortiAP 220B/221B, 11C