I'm doing the same thing at the moment, and yes, the quality of some of the feeds are really poor. You have to remember the way the system works is some volunteer, some distance from the airport has a police scanner or similar and just plugs that into their computer to upload to liveATC, and the liveATC network shares it about. There's no real standard to it, they just take whatever they can get. Let's be honest the likelihood that there are houses right next to an international airport is pretty low, and then there's the chance that someone willing to upload the streams lives in one of those houses AND has good, unobstructed line of sight? Some are worse than others, but quality will likely always be low to be honest. You often if you look at most listened to, that can indicate the uploader has a good reception.
My choice is VATSIM in conjunction with either FSX on my laptop or x-plane on desktop. I'm still very shaky and forget a lot, but it seems to be good practice! I believe IVAO is basically the same. It's not real ATC of course, it's an online community of amateurs, but most of them take it very seriously from what I've found so far. I know, I know, I'm sure I'll get hounded for it not being like the real thing, blah blah blah, but it's about as close as you're going to get at home.