I've had the HTC One m8 for about a month and love this sucker. It's pretty similar to the S5 AFAIK in terms of power, capability, and features (not waterproof, though). The One m8's camera is a little worse, but aesthetically this thing blows any galaxy phone out of the water. Best looking device I've ever owned. It's speakers are also WAY better than any other phone on the market.
You can't really go wrong with the s5 but the m8 is also worth a second look.