Hi,
i have S3 and can`t fault it. It`s fast, with 16 GB internal memory (you can extend it with microSD card), runs new Android. The only downside is the battery life, hence i got myself an extra capacity battery pack (lasts 3 days on one charge!).
It is good time to buy it, because the prices dropped (almost year old and the new S4 is due 26th of April).
Whatever You buy don`t go for Z10! It is my personal opinion based on experience.
As a somebody who work for mobile industry i had more than enough bad feedback about Z10.
There is new HTC ONE on the market, good phone but quite expensive (same as IPhone 5).
Regards