Summary: First of all, we note that these boards are aimed at different user categories. In particular, MSI P35 Neo3 is a "work-horse" with one PCI Express x16 slot, basic expansion options and minimum set of bundled items. Since it is priced at about $100, this product appears to be rather attractive.
The other board, Gigabyte EP35-DS4, costs a bit higher (about $170), and is aimed at PC enthusiasts.
Pros: high stability and good performance level;, two PCI Express x16 slots;, support for SerialATA II/RAID ( 8 lines; ICH9R + JMB363);, support for one P-ATA link (JMB363);, integrated 8-channel audio and Gigabit Ethernet LAN controller;, support for USB2.0 (12 ports) and IEEE-1394 (Firewire; 3 ports);, a rich selection of Gigabyte's proprietary technologies (C.I.A 2, EasyTune Center, FaceWizard, @BIOS, etc.);, support for Dynamic Energy Saver, DualBIOS;, passive system fo...
Cons: flaws in the software;, scarce package bundle., partial incompatibility to Corsair DDR2 TWIN2X2048-8500C5 memory modules;, flaws in the software.