one question about the 670 can I run mods(syrim/fallout/minecraft) less effectively than the 7970 because of the lower bandwidth...
that is a pretty subjective question and can be used for a bit of troll bait.
you will find that each card has better qualities that the other hasn't in different situations. but if you are going to go through them with a fine tooth comb; it will only lead you and other people to pull their hair out with indecision.
though to answer your question; the only time lower bandwidth comes into play is when 8x MSAA is used. other than that, nothing has been proven.