I have had the World Tour set since it came out and havent had any issues, except with my guitar. But I had a brand new one delivered to my house within a few days free of charge.
The drums arent of EXCELLENT build quiality, but they arent that bad either. They do the job.
As for Rock Band vs World Tour - Get the world tour hardware and rock band 2 software.
Rock band 2 has a much larger song library to download and i think the original track list better in any case. You can also import songs from RB1 and use them in RB2 for 400ms points. So if you buy and download a song, you can use them in any of the RB games sofar, whereas if you download a track for GH, it is limited to that one version of GH.
My current RB2 library is around 200 tracks and I wont spend another cent on GH tracks, because you simply dont use them anymore once you get a new verion GH.