I think you're talking about the Tekonsha
brand of controllers?
I have not used the Primus but I have used the Prodigy. They're both self leveling, have digital a readout, boost feature, self-diagnostics, and are adjustable. The only difference is the Primus is rated for 1-3 axles and the Prodigy is rated for 1-4. I have had my unit in two different trucks in the last 5 years and I have not had one single problem with it. One thing for sure is that I wouldn't want to tow my little 18' without it. It makes a big difference when we're driving through Denver or Colorado Springs as traffic comes to a stand still at a moment's notice. In my opinion, I don't think you can go wrong with any either of these units.
For more info, their homepage is http://www.tekonsha.com/product/default.asp
Where we've been:
2000 Rockwood Roo M-18 Hybrid
2006 Dodge Ram 2500 Auto 5.9 Diesel
Gone but not forgotten -1986 Rockwood 1003 PUP