In addition to what Akebono mentioned, the main features of the P5Q Deluxe over the EP45-UD3P are: Power and Reset switches on the motherboard (very nice when testing it), a LED indicates when standby power still is applied to the motherboard and it includes a hot-plug e-SATA connector.
On the other hand, the EP45-UD3P also is a very nice motherboard. Their implementation of e-SATA (not hot-pluggable) is very handy as it allows one to connect 2 SATA disks in the back (handy when copying files from another disk), the onboard sound is slightly better, it autodetects memory modules better than the P5Q Deluxe and it offers a better layout if you use lots of SATA devices (up to 10). If I needed another motherbaord, I'd probably go with the Gigabyte, but I'm not an extreme overclocker.