The TurboStick, both the US and JP version, has the most configurable autofire function of any control device I've ever encountered. In stead of just one, two, or three settings, you get a long slider to control how rapid the autofire becomes.
The JP TurboStick is better than the US TurboStick because the bottom is heavily weighted to keep it in place while you blast away. For some reason they removed the bottom weight from the US TurboStick for reasons I'll never understand.
Also, on the subject of TurboSticks, the device is called the "TurboStick" in both regions, but for different reasons. Obviously in the US it was to fall in line with the whole "Turbo-" family of products. In Japan I guess it was just in reference to the aforementioned ultra-configurable "turbo switch" functionality. The US version is black to match the TurboGrafx, and the JP version is a beige/grey color which doesn't really match anything else in the Japanese 'Engine line.
But back to the original question.
Spector, I find the "Blaster" 3-button pad to be quite pleasurable for shooter runs. It's a sleeker design than the official NEC 3-button pad, and all three buttons have the normal three-setting auto-fire functionality. This third button is great for shooters since it takes the place of "SELECT" (speed change) in games like Gunhed and "RUN" (player rotate) in games like Forgotten World eliminating a lot of the akwardness of using those buttons.
But perhaps best of all about this pad, is the D-pad has a "clicky" feel to it. It's hard to describe, but it's the same difference those older "clicky" PC keyboards have as opposed to the normal "mushy" key feel. During long shooter runs, my thumb gets VERY cramped up using a normal Duo/TurboPad pad and is sometimes immobile for a time afterwords. Not so with the Blaster... The D-Pad is easy to depress, and has a nice feel to it.
If you can fault the Blaster on any front it's that the pad borders on being too small. Bigger than an NES controller for sure but not as big as the NEC 6-button pad which is probably my favorite controller overall for the system.