Where are you doing most of your diving, and what are the conditions there?
For Puget Sound murk, the 21W HIDs are great. The focused 10W are a little anemic. The 12W LED is okay, but definitely doesn't have the punch of the 21W HID. It has other advantages, in terms of burn time and durability, though.
For backup lights, I'm quite fond right now of my Dorcys, which were cheap, but they do tend to turn themselves on at depth. I have to say that the best backup lights I've used (and I've owned a BUNCH of them) are the Halcyon Scouts with an LED module in them. They don't flood, they don't turn themselves on at depth, and with the LED module, they are good and bright and focused. We bought two old halogen Scouts on e-bay and put the modules in them -- they ended up costing about $50 apiece less than new, similar lights.