SSL VPN / LDAP VS. Radius

Hello,

I have my current SSL VPN setup using our Radius server.  All that has currently used VPN was staff.  We now have a need to allow vendors to also access the remote VPN.  I can't figure out how to create a Radius group that looks at which AD group is set in the Radius policy.  Currently the Fortigate is set to allow "any" members.  I tried to set a group name there which didn't work.  I then created a new user group based on LDAP which is working fine.  Are there any issues with using LDAP to authenticate users instead of Radius?

I am currently running 5.4.5.