I have used both Tommee Tippee CTN bottles, and Dr Browns. I am happy with both of them. The TT ones are easier to use, and are absolutely no problem to use, as long as your LO doesn't have colic. The teat collapsing thing only happens if the valve is stuck - you just need to squeeze it open gently (you usually have to do this with a brand new teat, but then rarely) and it's then fine.
Dr Browns are the best to help with colic, but they are a pain to clean/sterilise/assemble because there are lots of bits. They do tend to leak if the contents are hot - this can be improved a lot by loosening the lid, and turning the bottle upside down whilst at the same time tightening, and then shaking it upside down. Then always leave the lid a little loose anytime it's warm - apart from when using it for a feed of course!
For sterilisers, my main recommendation is to get a microwave one. They are easy to use and don't clutter your worktop as you can store it in/on the microwave when not in use. I have an Avent steriliser, which does the job well - however it is a bit annoying that the recesses for the bottles/teats are all the wrong size, so I'd also recommend getting the steriliser of the same brand as your bottles.
and the teats kept collapsing. 
