I've seen this question or implication of this question a number of times and I thought it would be worth an attempt at answering, as I've asked myself the same thing.
Last year I used my Bulldog SpiriT20 for T20, and in the past I've used normal bats. This year I'll be using the Laver Ultra.
What's driven my decision? Well, as always, it's complicated! Fundamentally though, it's actually the bat that I feel most happy with trying to score runs quickly with.
In the nets in the run up to both seasons, I have tried to use my T20 bats with a requirement to score runs quickly, and what I've found has been that the bat that I've been most comfortable doing this with hasn't always been the bat that I thought it would be. Generally, it's been manoeuverable and easily used, as the key aspects, and of course has to have great ping and suit the T20 pitches I play on.
Now realistically I know that my Instinct is just as capable as the Ultra is in this approach, after all, I've used both in the nets, and know how they both work, but if I'm honest, using the Laver against the T20 bowlers that we have feels better, and I seem to hit the ball harder.... The sad side effect is that I am now slipping into different bats for different games.
Does this really mean that actually I'd do just as well with the Instinct in T20 and I'vevjust used the Laver more in the run up to the season? Hmmm...