On average, with no other factors, I’ll say no. But you’ll get those nice moments when you fire off 6 shots in the span of about 3.
But, it’s not actually a choice, because the alternative to Hell’s are not 9% Fire Rate per 1 skill point.
You will have other Fire Rate. Which actually makes Hell’s even better, because it works with your Fire Rate. The faster you fire, the faster you get Extra Shots. You might say that Hell’s multiplies your DPS by 1.45 on average at 5/5.
That may not be specifically accurate, because I seem to recall that the game counts Fire Rate Delay from the Extra Shot and not the normal shot (which is why people thought Two Fang didn’t work over 10 FR).
But it’s more accurate than saying it’s a Fire Rate increase.
If you want a more numerical answer, I could give it a shot, but it would take me some time because this isn’t something I really tackled before. The main odd bit would be considering the Fire Rate of the Extra Shot and accounting for it in the timing for the next normal shot.
But to return to your original question:
“Is X% Hell’s better than X% Fire Rate?”
I’ll respond with a question:
“Is X% Type B Critical better than X% Type A Critical?”
I think this illustrates the question in a light you’re more familiar with.