iOS is probably the better OS in most respects, as it only needs to cater to their own products who's tech specs are rather limited. iOS is very restrictive however.

Android caters to all kinds of specs and not just their own limited spec products, so can be found to be lacking in certain aspects. The tech specs of android phones tend to be far more up to date than iphones though.

iphones are also a rip off for the specs you get. You have to pay a high premium for the brand.