My personal line in my head for a "Speed bow" is anything rated 320fps or higher IBO. These are generally the more radical cam, higher reflex, lower brace height genre of bows.

And remember just because a bow CAN do a certain speed doesn't mean you have to shoot it that fast. That's where higher performance has some advantages. Shoot a heavier arrow the same speed as a lower performance bow for a boost in KE, or shoot a lower draw weight to get the same speed from the same arrow as a lower performance bow.
You can choose to give yourself more energy or do less work to get the same results, or both in some cases.

Its always nice to be able to SLOW a bow down because you have that luxury.........there aren't many practical options for SPEEDING one up especially if you are already at 5gr/lb and want or need to go faster.

I'd rather have it there IF I need it or want to use it than wish i had it in the first place.