The TD-20 costs £4,500 compared to £1599 for the 2Box, so its not really fair to compare them. I wouldn't say the 2Box is better, just different. For instance the TD-20 (and most Roland modules) have many features that the 2Box does not have (positional sensing, abiltiy to create drumkit chains, ambience and effects, compression, equaliser etc, sequencer, etc), so in some ways it is a far more advanced piece of equipment.
The main problem that comes up time and time again with v-drums is that the COSM system just doesn't seem to make realistic sounding accoustic drums. They stick out like a sore thumb in music, you can recognise them straight away. I've seen tons of music DVD's where the drummer is using v-drums, and you can always tell, and it always sounds jarring. The 2Box doesn't have this issue because it is using samples of real drums rather than having an algorithm to emulate them. Also v-drums are closed system, you can't really change whats in the module. With 2Box you can.
So it really comes down to your needs. I had v-drums before and they do some cool things, but what is missing is the 'real' sound of accoustic drums. The 2Box solves this issue, and personally thats what I wanted, a module that had really strong accoustic sounds. I don't need fancy effects or sequencing on board, I just wanted an e-kit that could sound like an accoustic on stage and at home, and still allow me to use my own sounds without the need for a PC or laptop.
