I have the ST-200. It's about the most accurate and fastest tuner around. It's quite solid and very small which is good if you decide you are going to mount it on a pedal board.
I also have a Boss, I forget if it's a TU-2 or TU-3. It works fine but if I could only have one pedal type tuner, it would be the ST-200. The accuracy of it will become more important as your ear improves and when you want to set up the intonation on your guitars.