I have used crap grocery panniers (from Nashbar) and expensive grocery panniers (from Jandd). The crap ones, well, crapped out pretty quickly due to cheap construction. In both cases, they were designed to fit exactly one brown paper grocery bag. But if you aren't packing your groceries that way, you don't need to use a grocery pannier and regular Ortliebs or something might be a better choice. Or just a big backpack, depending on how far you're going.

I'm not inclined to use wire baskets, but I've never tried them, so what do I know? My understanding is that they don't hook on, they bolt on, and for the way I use my commuter, I wouldn't want them rattling around the rest of the time.