There are significant differences between both motherboards. Will you overclock? I presume so if you selected the Maximus II Formula. Is the type of memory (DDR2 or DDR3) important to you? Answering those questions should help you decide. Would I buy one of these motherboards? Probably not. Have you looked at less expensive motherboards like the Asus P5Q Deluxe or the excellent Gigabyte GA-EP45-UD3P?
intel dp45sg motherboard is built to support the latest Intel® Core™2 Extreme processors and DDR3 1333 with overclocking features that bring extreme performance to your gaming and home entertainment machines. With the full-size ATX form factor, you will have incredible expandability options, including dual PCI Express* 2.0 x16 slots, up to twelve USB ports, eSATA, and more.As many more good features are there so as i can say it is the better one.