Vatsim or NOAA?

I'm sorry for what is probably a newbie question but I sim always offline. Well I'm connected to the internet but you get my point. Should I use vatsim or noaa or IVAO, I believe it's called or what? Also I have less problems or seem to when using just FSUIPC and not combined with simconnect. Is this okay just to use this option? Thanks for indulging a newbie to trying to get real world weather back!