It's not really an either/or. For scoring purposes, it's BOTH overall and per card.
In your situation, the overall util is the main thing. $75 used over $1,500 total lines gives you a util of 5% if I'm doing my math right this early in the morning. And that's the most important figure.
$75 on a $400 CL card also gives you 19% util on that card. 19% util on one card won't help you or hurt you particularly.
But let's say you let a balance of $375 util report on that one card and still had zero on the rest. Then you'd have an overall util of 25% (which is also not bad, though MyFico people will scold you for it). But your util ON THAT ONE CARD would be almost 94% -- and alarm bells would go off in the scoring systems because that's considered maxed out. Having any card, even one card, maxed out, gets you a ding in your score.
So the simple answer: utilization is the overall balance to your overall credit. But individual card balances are also watched and considered in scoring.
