Because it was just after my 18th birthday, so I had a far bit of money so I thought if I had the money I may as well get the best that was available...
I did look at the differences between them. I thought the heatsinks of the deluxe looked nicer and would perform better. I also thought it had 'cooler' features, such as the LED post indicator and thunderbolt - not that I'd be using it anyway. It also has a better power phase system for better overclocking so far as I'm aware.
It probably didnt really justify spending the extra money on it, but I wasnt exactly short at the time and I'm so so glad I did get it.
I also built a PC for a mate of mine, initially using the gigabyte ud5 wifi. Because of his TV however, through HDMI the BIOS wouldnt display properly, which we then thought was a motherboard issue, so we RMA'ed the board - even thought I'm still sure there was nothing wrong with it. Still, the mugs at ebuyer accepted it
He was going to buy the p8z77 pro, but he'd seen mine, and did also think the extra wifi antenna may be useful, so he got the deluxe instead.
Through 2 of them now, despite them being a fair bit more expensive than some similar ones, I honestly believe they are worth it. We havent had a problem with either, the BIOS is very easy to use and the built in wifi is by far the best I've ever used. I have also used a £50 belkin pci card which despite being an excellent product, the driver support was not there. With this the drivers have been fantastic and I've never had 1 bar drop of signal through use, never had the speed decrease whatsoever nor have I had any random disconnections like I previously have with wifi adapters. As it's built in, it also doesnt take up a pci lane or a usb slot which does make things pretty easy.
I was only ever going to buy one of the asus or gigabyte boards because I did think that on board wifi would be far better than a secondary card, and I am so glad that I did buy this in the end.
I dont want to be taking anything away from the other manufacturers as I'm sure they're good too, but because of this, my next board will be another ASUS I'm sure