Hmm actually a tough call if you don't have enough coins. I always have enough coins every week to buy everything I want lol I would def say buy Icebreaker, you will regret it. However armor can be just as rare, example he has only sold Helm of Saint-14 once so far and everyone who didn't buy it regretting it. I personally have ice breaker (originally bought from xur) and found two more after, I can't say you will have the same experience as I but Icebreaker is not an end-all weapon, there are a lot of snipers out there that are very useable and don't require an exotic slot. Especially when you consider how common special ammo drops.