I just went through what your going through. I found out a few things. One You get what you paid for. That being said, I found that the back up light was not so big a deal as the primary was. I was given a Princeton tec c-8 for Xmas. Second dive, and the first one at any depth, it flooded, and some damage was done before I noticed it. Bad news, I didn't think it was very bright, and was unfocasable. Good news was PT said to send it back and they woud fix it. They sent me a new one instead. In the mean time I needed a Dive light so I picked up a used one for 20 bucks on Ebay. It was a Underwater Kinetics d-8. (was a pretty pricey light when new) Now that's a bigger light, but boy does it work well! bright, beam really pierces the water, so far has not leaked and seems to be a better built piece in general then the PT light. I looked into the canister lights, but that is too pricey for me so that limited my choices some. I would buy a UK over PT only due to my personal experiences so far. I also have noticed some folks have lights on their Primary regs, so you can locate each other, that looked like a good idea, even though I don't yet have one. And the one I really need to get is a strobe for hanging under your boat. You can't believe how hard it is to find a boat at night! and then get the right one. Sounds easy, but it can be a challenge. I liked the newer models that have switchable bulbs built in, gives you just a bit more redundancy. And make sure it has a lock on the switch, I had one turn on in my baggage. New rule for self: take out the batteries while traveling stupid! or lock the latch. I had left the batteries in due to space constraints in my baggage. Good news is it didn't melt anything, but it was hot when I found it.
Like I said, I just got started on this light business, but I did learn a bit in the process.
