so im gonna build my own pc but i want the motherboard to be ati crossfirex ready...now ive found this board Gigabyte GA-MA785GT-UD3H and it says its got ati hybrid crossfireX is this the same as normal ati crossfireX ???
No hybrid crossfire will crossfire the IGP and the discrete card, only really helpful for low end discrete cards, if you want crossfire you need one of the following for an intel build P45 and P55 will provide 8x/8x crossfire and the X48 and X58 will provide 16x/16x crossfire, for AMD builds the 790X and 790GX provide 8x/8x and the 790FX board provides 16x/16x crossfire.
If you look at the lower chart on the link I provided, you'll see that the 790GX chipset allows you to use any card listed in the upper chart in a CrossfireX combination (including the HD4870). The upper chart also shows that the HD4870 can only be paired with another HD4870 (normal Crossfire) or an HD4870x2 (CrossfireX).
Whether or not it's better depends on your intended system usage. If you gaming at high resolutions with lots of eye-candy, the definitely, the 790GX motherboard is a better option.
From what I can see it's just another version of the 4870 from XFX. It's performance should pretty much be the same. I don't know why you are finding it for cheaper though, where are you planning on buying from?
http://www.pchardwareuk.com there is like 5 type of different 4870 and i dont know witch 1 to buy....its got ATI RADEON HD4870 750M 1GB DDR5 DUAL DVI TV LITE VERSION for 112.63gbp and the ATI 4870 HD4870 1GB GDDR5 TV DVI X2 HDMI 109.81gbp or theres XFX/ATI Radeon HD 4870 1024MB PCI-E 2.0 HDTV/Dual-Link DVI Graphics Card for 115.54gbp and im confused as to what each of them has that the other hasnt to make the prices different