Phenom II x6 1055 is able to crossfire 2 seperate GPU in dual x16, no bottleneck.
i5-750 is better with crossfire when that's 2xGPU in 1 lane, if crossfire 2 seperate very-high-end GPU thus 2 lane together there will be bottleneck due to dual x8 but not noticeable.
From my point of view, they started to produce more 2 in 1 GPU due to better scaling, less power consumption, less heat, just 1 lane. A very good example, HD 4870 X2. So crossfire 2 seperate GPU is not a better choice and only option for those who want to try around what is crossfire.
Anyway, i5-750 can handle this HD 4870x2 well with no bottletneck.
Here's the latest graphic card hierarchy chart http://www.tomshardware.com/reviews/graphics-card-radeo...
Yes both can crossfire and sli, this question is more dependence on mobo.
2nd: Which of these two are better for using 2 GPU 's ?
3rd: Can both of these use Crossfire and Sli ?
P.S. Can you answer each question individually, and price should not be factored into the answers
Thanks so much,
 If the cards are mainstream, like 5770/gtx 260 or something, then no difference between 750 & 1055. So based on previous, 750 still wins.
For high end cards, there would be a slight difference. But not enough to tip th scales in the balance on 1055t.