I have both an underworks tri top and a tri top gc2b binder. I've had them both for around the same time (2/3 months), but the underworks has stretched out quite a bit so I only use it for sleeping in, wheareas the gc2b one hasn't stretched out at all, not sure if that's bcos I wash it and wear it every two days, then switch it with my other gc2b and do the same. Even when new it didn't bind nearly as well as the gc2b binder (I'm a uk bra size B). The gc2b is also very comfortable, I wear it all day and my ribs never hurt, I can also breathe comfortably in it(able to take deep breaths when wearing it). I don't think this binder will damage your chest as it is so comfortable. Overall I recommend the gc2b.
Ps, with the gc2b binder you have to measure yourself exactly and go with the corresponding size, with the underworks however you have to go up an extra size to the one their chart is telling you to buy otherwise you won't be able to get it on.