Client side certificates vs dual factor authentication

Please can someone clear this up for me. Are client side certificate connections less secure than DF authentication? I am proposing a VPN solution to a client, using OpenVPN software, but their offshore business IT dept has claimed the connections need to be a minimum dual factor authentication.

I am trying to allow my clients' business partner's specific users, remote access to a PC on a separate network (my clients'), accessing an application over remote desktop. I had recommended OPenVPN, which can be configured to only allow access to the server "host", and will not push out routes to the rest of the network. However if they access the PC via RDP, I guess they will have some access anyway, but that is not a security risk to themselves...(business partner)
They also need access to a OpenVMS server on the network, so I need to somehow allow for telnet access...

Anyone have any ideas on the best way to accomplish this? I heard of Juniper SSL VPN devices, that may be able to accomplish this - but are they difficult to configure?
I suppose I am getting off the subject, but any assistance is appreciated.

Thanks,
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