I would also use the 850 Platimax, mainly because of Enermax's long standing reputation for delivering consistently quality products. I would not hesitate to install one in my system.
I would use the Platimax 850W PSU because it would have plenty of power for the rig I'm building my son for when he comes down to visit me this summer.
If I were to win a new Enermax powersupply I'd still continue to use my old Modu+ 82 since it has been running great for almost 2 years. If I were buying today however, I would more than likely go for the 850w Platimax model.
Really I think any of their 800+ power supplies would be perfect for my next build and are on my short list as power supplies. Of course if I actually manage to win this it'd be this 850 watt model.
I would use this for my current rebuild. I'm going to give, my 700D a nice silver and carbon fiber theme. That and this cm unit sucks and on its last legs with its crappy unstable voltage...
I'd get the ENERMAX NAXN 82+ ENM750AWT 750W for my next build. Don't need more power than that and it's about time I try one of Enermax's modular PSU's.
I would use the 850 to support more hard drive storage and a Crossfire that is in the planning stages. The power efficiency doesn't hurt either, and the modular cable design would help my cramped case breathe!
I'd use the Platimax 1200 because it's a great power supply and provides a crap load of clean, reliable power. And besides that I like to run multi-gpu machines overclocked to the max pulling lots of watts.
I would use the ENERMAX MODU87+ EMG700AWT 700W for my current upgrade plans. The modular cables would make a cleaner build and provide more than enough power for all my components and case fans.
I would enjoy having a modular PSU that reduces the cable clutter and the 850 watts would let me consider adding a second GPU to my system. I have used Enermax in the past for both case and PSU with great results!