Performance wise the Core i7 860 will be generally faster (see below though) and probably has more scope for overclocking.
However only video editing will really benefit from multiple cores and then only if the software you use firstly,is multi-core aware and secondly, can make use of Hyper Threading in the case of the Core i7 860. If this is the case then either CPU would be fine. The 1055T would probably be the faster CPU for video editing but unless you do loads then I doubt you'd notice much difference.
As your main use is gaming I would suggest the graphics card takes priority in your decision. After saying that unless you game at high resolutions then the 5850 could well be fast enough. However if you want a bit of future proofing for new games releases then the 5870 might be better.
I think you'd be happy with either of those systems.