As you can see from the
SmallNetBuilder Charts, there's not much to choose in performance between the different makes of 500 Mbps units, almost all use the same basic chipset. The two exceptions are the latest Zyxel and Netgear units which use a newer chipset. It's probably worth spending the extra on passthrough units, as they can usually be plugged directly into a wall socket without adding an extension cable (which causes a performance hit).
One thing to look out for is where your wall sockets are located. I once had a problem with some that were mounted low down on the skirting board. This meant that units that had the main plug at the top and ethernet cable exit at the bottom (like
these TP-Link ones) wouldn't fit, but I was able to get some
Netgear ones with the mains plug at the bottom and cable exit at the top that did fit.
As bubblegum57 says, don't expect anything close to the rated link rates in terms of actual data transfer rates. The SmallNetBuilder reviews give a reasonable idea of what you might expect in a typical installation, but look at the difference in performance with location of the homeplugs - it drops significantly the further apart they are.
Personally I use a pair of D-Link 500Mbps units (now replaced by a newer model), but I've put in TP-Link, Netgear and Devolo units for family/friends and from my (admittedly small) experience there isn't any real difference in build quality and reliability between the brands.
