There are other several other faults in Guitar Hero World Tour apart from the drums.
The gameplay is not what you'd expect. The songs in Guitar Hero World Tour are not really that good. I only found 3 songs in the whole songlist that I could recognize. It's your choice though, a cheaper drumset is not worth it to me. Here is a list of songs that are in Rock Band 2:
List of songs in Rock Band 2 - Wikipedia, the free encyclopedia
Here is a list of songs that are in Guitar Hero World Tour:
List of songs in Guitar Hero World Tour - Wikipedia, the free encyclopedia