Whichever quality chain lube you like. Your choice has very little to do with drive train efficiency and everything to do with wear. Find one that will last as long as you want to go between applications.

I use Dumonde Tech on my mountain bikes, Dumonde Tech Lite on my road bikes, and Phil's Tenacious Oil in the winter. I reapply every 20 or so 25 mile commutes or 10 or so longer rides and use whichever lube generally lasts that long. I didn't like Pedro's Extra Dry, which I guess attracted dirt because it wasn't dry enough, or White Lightning which never seemed to last long enough to reap the benefits it supposedly offered.