this is probably an easy question for most of you but I have no Idea I've never come across anyting in my local store but roundwounds. I sort of understand the differnce between roundwound and flatwound, but what is groundwound and what sort of style are they suited to?
Ground-roundwound (GRW) strings started life as larger RW strings, and were then had the outside ground smooth. FW strings are built of a core that is wrapped with flat metal tape (which doesn't bend very well so poor sustain). GRW sound a lot like RW without so many highs, and little finger noise. I find they sound very "clean" and cut thru a mix fairly well, while FW did not for me. They sound like dead RW strings that then hold the same tone for years. According to a local poll, I'm in the 2% that likes them. I play classic rock, but I think they are suitable for anything that doesn't require a lot of slap/pop work or extreme highs. If you want to experiment with GRW, try GHS Brite Flats; abour $28 from www.juststrings.com .
I use D'Addario half-rounds (same as ground-wounds) and D'Addario and Fender flat-wounds. If your looking for solid thump, low sustain, and not a lot of highs (treblely tone subdued), the flats are the best way to go. I have them on my AmStd P-Bass and won't run anything else on it. If you, like me, can't stand the high trebly content of round-wounds, the high finger noise of round-wounds, or the sandpaper feel of roundwounds, then try the half-rounds. They are a good compromise. I use them on my AmStd J-Bass and really like them. Many like round-wounds which explains why there are more versions of round-wound strings than the others. However, there are enough of us who don't that various manufacturers produce the flats and half-rounds. I've tried almost every brand available at one time or another, and for my money, D'Addario and Fender produce the best flats, D'Addario the best half-rounds. Invest some money, try them out. Everyone likes a little different sound and feel, so, only you can make the final determination for you. Good Luck.