You need the one to match the VDO gauge. If you use the MFA one you'll get perculiar results. I'm using the MFA one with my VDO gauges and its reading 140 degrees on the VDO, if I swap it back to MFA I get 100 degs.
I don't have the VDO sender, I'm having to get the seller off eBay to post it me out so that I can pop that in.