Ahh thanks jolly. I thought it was weird... I was sure I was hitting different serves!
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It's all semantics.
They're hit differently and they react different, but it's all just different flavors of the same kind of serve. They only real difference is that they have the spin axis at difference angles.
A twist serve (in my book) is any spin serve that is somewhere between topspin and slice, usually closer to topspin on the second serve. A 'topspin slice' would be a twist serve closer to slice. But it's still the same kind of serve, regardless of how each specific version is hit... changing the ball toss or the swing pattern doesn't mean jack if you're talking about the same concept. And the reaction on bounce will be different too, but that's because of the angle of the spin axis on the ball (and or the amount of spin generated), NOT because of some arbitrary label you've put on the ball.
The closer the spin axis is to 'slice' (ideally horizontal but that's not going to happen...), the more aggressive the shot, and the more lateral the bounce. The closer to topspin (vertical, or straight up), the more reliable the serve becomes, and the more vertical the bounce becomes.
It's all really just settings on dial, so to speak... but where you decide to call one shot topspin slice, one twist, and one shot slice topspin is totally irrelevant since everyone is going to have a different definition.