I double tap. I don't see anything wrong with doing it either way. It's kind of like the difference between driving a manual and an automatic. One is a little easier to handle, but you feel you have more control with the other. I prefer the control personally. Also, I tend to keep 4 songs up more often then not. There's so many contributing factors though, lag being a big one. And since so many things can cause lag, your 4-twist (or even 3-twist) can get messed up pretty easy. If you want to be successful at 4-twist though, my recommendation is to learn not to depend on the casting bar. Use it early on to learn your timing, but by the time you're in your 40's you shouldn't need it as much. That way you can twist even when blinded. It's also good to learn to twist based on timing instead of the casting bar because procs can cause your bar to "poof". It doesn't change the timing of the cast or even interrupt it, but procing in the middle of a cast will cause your bar to disappear, making it look like you fizzled, when in fact you didn't. Things will change quite a bit though post-50. As with all other classes that cast, you will fizzle much more often for some reason, even on low level spells (at least it seems this way to me, and pretty much everybody I've talked to about it. Maybe it's pshycological...).
Basically, it doesn't really matter if you twist 3 or 4 or if you use a macro or not. 3 doesn't make you a worse bard. The bard is a very involved class. Song selection and instrument/weapon selection can make a HUGE difference, and just knowing the nuances of the class will get you a lot of respect and a lot of enjoyment.