Rocky, is a percussion version a new addition this year? The Firestorm used to only be available in Flintlock:
A blued and a stainless version, both Flintlock, both with synthetic stocks.
To your question, most inlines are built with a fast twist designed exclusively with the sabot/bullet in mind and typically won't shoot round balls very well.
The Firestorm has the 1:48" twist as a compromise for use with round balls, conicals, and sabot/bullet combinations, typically shooting all of them very well but very rarely all of them at competition levels.
If your main interest is hunting and flexibility in choice of projectile, the 1:48" twist is hard to beat...I have 1:48's in .45 and .50cals and they shoot cloverleafs at 50yds with full power hunting loads using RB's, Maxi-Hunters, and sabots/bullets