PPTP: RADIUS or Windows Authentication?

G’day everyone

When configuring PPTP VPN service via RRAS on Microsoft Windows 2000 server you have the option to use Windows OR RADIUS authentication. First, I know what RADIUS is but I am confused about which one I should pick and why? Which isthe most secure?

Here is how I see it. With Windows Authentication, when a remote user contact the PPTP server he provides his domain user ID, password and domain name and then RRAS goes to a DC and validates the access. If I choose RADIUS, it istransparent for the user but behind the scene there is a middle man, right? RADIUS receives the login credentials and validates against a DC. From my point of view, this sounds like a proxy service, am I right? RADIUS adds a step in the equation, but does it worth it? Please clarify.

Best regards
Patrick.