The iPhone 5 is the newest and has the latest and greatest LTE modem from Qualcomm (MDM9615M) while the others are on year old stuff most likely (especially the hotspot devices).
And he doesn't say whether he was tethering on the iPhone/iPad/Galaxy Nexus, but going over two wireless networks instead of one for the hotspots could also be killer.
Unfortunately even the (supposedly international) GSM iPhone 5 is mostly tuned to LTE frequencies commonly used in the USA. In Germany we have multiple 4G frequencies and the new iPhone 5 supports exactly one of them (by T-Mobile, the other carriers have zero of their spectrum supported by the iPhone 5). In other European countries it's even worse.
Especially the 800 MHz LTE band would have been useful. This band is used in rural Germany to provide LTE based broadband to homes where DSL or cable based internet is unavailable. If the iPhone had supported it you could suddenly have really high bandwidth connections in rural areas where you now only find some crappy EDGE connections.
Weird, my dedicated 4G hot spots always work better than tethering through my devices. If he jailbroke the iOS, then tethered through it, I don't think its advantage would hold up.
On another note, I wonder how long until we see dual simultaneous antennas (and modems and whatever it takes) just to win the spec war on this. amazon already did it for Kindle with WiFi.
The SGS3 4G only just launched in Australia. The one that has been on sale only supports HSPA+, referred to as 3G or 3G+, depending on who you talk to, so it probably is only 'barely above 3G'.
While 4G isn't available here, I was at least happy to see 15 mbps reliably on 3G. For my typical use case, e.g. checking tweets and casual browsing, I don't miss a better connection. (For tethering it sure would be nice, though.)
And he doesn't say whether he was tethering on the iPhone/iPad/Galaxy Nexus, but going over two wireless networks instead of one for the hotspots could also be killer.