The pixel resolution of the S5 Active’s display isn’t changed, so it’s the same 1,080 x 1,920 that’s also seen on the regular S5. The larger screen is hardly noticeable if you put the S5 Active next to the original S5.
According to TK Tech News, the S5 Active is IP58-certified, thus providing the same levels of dust- and water-resistance as Sony’s Xperia Z2. The regular Galaxy S5 is IP67-certified, which means you can’t keep it underwater for more than 30 minutes (but you will be able to do this with the S5 Active).
The unannounced Samsung Galaxy S5 Active SM-G870A
source: TK Tech News (1), (2)