I don't think Apple really provided any wow factor past the ip4 days when they had that incredible front/back glass hardware. They just excel at making things work in synergy and not having to tweak or dig around settings to get things to work. While Android has made incredible leaps and bounds it still has a lot of what I like to call "turds" that come up every now and then that need to be ironed out, turds which affect functionality and cause frustration IMO. That's why I still use an iphone as my main phone because I just need to get things done with no messing around. Of course I also carry around a Note 3 as my "play" phone, for tablet use, consumption, tweaking, etc.
A larger screen iphone is going to be seriously powerful in today's consumer market. Samsung and others need to step up their game and introduce something very novel because a large iphone is really going to eat their lunch. I can't see the S5 really competing very well as it doesn't really have anything really "wow" about it. It's a nice phone and it certainly hits all the checkmarks for a flagship, but I can only see it competing in price IMO.