PPTP is an unsecure Microsoft protocol !
OpenVPN uses SSL to encrypt the tunnel and is if you use PKI very secure.
I would never use PPTP over OpenVPN.
I would rather drop PPTP in m0n0, to get openvpn
Are we still in 1999?
I think a lot of those brute force attacks you are referring to were patched last century. Go grab the L0phtcrack software and see how easy it is to actually break the encryption on it now. Last I checked, waiting a hundred years for it to finish an offline attack was not realistic for me when I tried. Sure, it can be broken, but until we all have super computers at our disposable, I'm not going to worry about a hacker at a local coffee shop.
I'm sure the OpenVPN is more secure, but saying that any encryption is invincible, well we all know better than that. OpenVPN may take a million years to crack, but how feasible is it really for either?
I'm sure that m0n0wall has the latest updates that go for the PPTP, so I'm not worried about my encryption. Yeah, it's a Microsoft thing, I don't like them much either, but I hate it when FUD is spread around for anything. If m0n0wall goes to OpenVPN, great too.