Both are very similar boards. If you are planning on using multiple video cards, the ASUS Maximum VIII is a better choice with 2 PCIE x16 slots. The Gigabyte has only a single X16 slot. The ASUS also has a comparatively better sound card (8 channels vs 5.1), but that depends on your existing sound system. All other points, such as usb slots, SATA ports, etc. are very similar.
From a reliability point of view, the Gigabyte is considered more reliable than the ASUS. My suggestion is: decide which one fits your needs more. (SLI gaming or not) Then choose which one looks better. ^^;