if your hub is distant, it could simply be that the signal you're getting to the tv isn't good enough - that could either be a crap hub, or something interfering with the signal. if you've bought a recent stick, it might simply have a better wireless chip in there that gets a better signal. if you have more devices on your network now (and most people do over time), that'll slow things down, too. also, buffering tends to be network related rather than anything to do with the tv - it might be that the connection you have is experiencing more traffic now, too.
in general, though, go for a roku stick - it's the only device that'll give you all of the providers (amazon, now tv, netflix, google).