Danny,
At first it seemed to me the T3 and T4 did not sound very different. It wasn't until I really got into the T4 and started using various voices together with the on-board styles that it became clear the T4 had a lot more to offer. I was playing my T3 setups on the T4 and they didn't sound much different. There was a very definite difference in the quality of sound produced by the T4 that the T3 did not have when using the onboard sounds and styles. It wasn't the kind of difference that jumped out and knocked your socks off but there is a difference.

Hope this helps.

Deane