For ETF, where you run a card 24/7, I take 3 things into consideration.
1) Power efficiency. You don't want to run up your electricity bill or cause global warming. Otherwise I'd run my VEGA 64 with the power limits unlocked at 1800MHz.
2) Overclock headroom. The handicap multipliers are based on the LARS database which is supposed to be based on base clocks (really it's random as hell). The winners will be the cards that overclock to perform much higher than the LARS baseline. We have figured out that it's best to run a card for a week or so at stock clocks with the LARS dark mode enabled to feed it baseline data before you enter it into competition. Then be sure to disable the LARS dark mode plug-in when you run overclocked or you will bork up your handicap like I did a few months ago because I didn't know any better.
3) Can it effectively complete WUs in a reasonable amount of time. I'm having this problem with my GTX 750. While it is efficient and overclocks well, it seems to have some very gimped compute performance. I'm going to switch back to my HD 7850 as soon as I get my water loop rebuilt, hopefully this week. Michele is having the same problem with her GT 730 so I ordered her a GTX 465 for $25 on ebay. Supposedly Fermi has good compute performance and that model has good OC headroom (in theory) since it has a huge portion of weak shaders disabled from the 480 core.
lol the first picture with the baby MSI card actually has all power connectors plugged in, because there's only 2, the CPU and motherboard.
I'll take some more pictures this week. If you are curious, it took me about 2 bars of aluminum angle which I cut into 10 inch pieces to fit the 9.5x9.5" mATX motherboard tray. This time I used rivets instead of screws to fasten it together and it's very strong.