Would this mean that Antminers are all around the better usb asics?
Pretty much. I vaguely recall some people having issues getting a bunch of them working on the same USB port, comms-wise at the computer end, but even so.. a single Antminer U2 is basically as fast as 5-6 Block Erupter USBs.
I notice many people use block eruptors in their mining rigs, so I want to know why they would use eruptors when you could spend a couple extra bucks for a Antminer.
They probably already had them, or they found them to be available cheaply ($5) and easily (available just about everywhere). There's even sites that will sell you a bunch of them + hub + fan as a package deal.
It's also entirely possible that they don't do the math and are thinking they're building one heck of a mining rig based solely on the number of miners they've got plugged in - or they don't care to do the math and just build the rigs for fun - like I said, neither is going to ROI unless you play the lottery with them, so you might as well do it for fun.