Swords of Fury isn't easy to find, especially in decent condition. Sure it's easy to roll over (being the last 7-digit game made by Williams) but it's the kind of game that has a cult following. Many of them have a cracked right ramp; I keep hoping someone will remake the ramps for it eventually. Productionwise, there were ~2700 Swords of Furys made compared to ~7300 for Whirlwind, so I'm guessing you'd probably be able to find another Whirlwind sooner than you would a Swords.

Admittedly I'm biased, Swords was the first pin I bought back in 1997 and I intend to never let it go unless somehow I found one in better condition.