I previously had an iphone 4 before I replaced it with my GS4. It has identical wireless performance, this invisible cap of 25mbps down. I personally have 100mbps shaw cable at home, it speed tests over 100mbps down and over 5mbps up on a wired connection and over 95mbps down 5mbps up on a wireless connection on a PC.
I've tested both the 2.4 G and 5ghz wireless N on my dual band router, made no difference. Do these phones only have 54g support? I'm disappointed that a new device with other high speed features such has USB 3.0, LTE and apparent wireless N 5ghz support still cant take advantage of real high speed wifi connections.