I have both devices. I haven't really started playing with them yet but out the box the hsg-x5a seems better in quality and stability. It doesn't have a gsensor and since mines is a earlier version i don't have the market and gmail installed. (if you find a rom to upgrade it let me know). The zt180 touchscreen seems smoother but its very buggy. I haven't upgraded to 0804 yet but will try it out soon