AFAIK,Adobe software tends to run better on Intel CPUs.
In this review the Phenom II X6 1055T is ahead of the Core i5 750 though in Adobe Premiere Pro CS5:
In this comparison the Core i5 750 is also slightly slower than the Phenom II X6 1055T in Adobe Premiere Pro CS5:
However,the Core i5 760 maybe around the same speed as the Phenom II X6 1055T.
OTH,the cheaper AMD motherboards mean you could fit a Phenom II X6 1075T which probably would be quicker than a Core i5 760.
For transcoding if the software can use six cores the Phenom II X6 1055T and 1075T should be faster
IMHO than a Core i5 760.
For multi-tasking the Phenom II X6 should be faster in theory as you could dedicate individual cores to certain tasks.
The Core i5 760 would be faster for gaming when compared to a Phenom II X6 1055T or 1075T in most cases.