I love my carbtune tool. I went through the same thing last year: "Do I really want to spend $100 on a tool I'll use so infrequently??"
But I wound up syncing my carbs 3 or 4 times in the last year for various reasons (tuneup, new cables, had manifolds off, etc), and also I will be using it on my next bike project as well. I think it will pay for itself because it gives you the freedom to use it how and when you want.
That said, I have not tried the dial gauge syncronizers, I'm sure they're fine. I really like the carbtune for its idiot-proof ease of use (and I am a supreme idiot when it comes to carbs). It's also a nice sturdy tool, I think it will last me a long time. There's no calibration, no fussing with fluids like the motion pro tool, and it's really simple.
If you were in New England I'd let you come over and use it. But you're not, so I can only recommend buying one.
Good luck with your tuneup!