More chances of bargains with BINs, because if you spot them the moment they are listed you can grab them there and then of course ... but Scott's right, if you can be bothered putting in the time you will still find good coins at low prices in auctions too, maybe through listing errors, poor pics, mis-attribution, and so on
I can't be bothered trawling though them all any more, I look at newly listed early milled and hammered once or twice a week, knowing I will miss some and occasionally get lucky