I had 2 FQs, a 15 lb and a 16 lbs.
I used them on medium-light to medium oil patterns, in general. I could use one on slightly heavier, depending on the drilling. I drilled it flippy, with longish pin-to-PAP distance, 5" once to be able to use it on medium-light oil patterns, but that made the 15 lb fine but the reaction of the 16 lb was very problematical with that drilling. I'm guessing the difference was varyings RGs and RG differentials with the different weights.
Overall the ball had a medium hook with strong, continuous backend, given the generally fairly low Rg differential, which is the major factor in determing how much flare a ball produces. So, this ball was much stronger than its RG differential, a low .032, would ever indicate.
PK 18, in the vaguest general terms, goes longer than PK 17, but has a stronger flippier larger backend, IF you had to define such a relationship. Since for the 99% case, you won't find these two coverstocks on the same core, you can disregard that comparison. The cover/core define what a ball is designed to do; drill it and use it according to that.
Remember your hand determines how the ball will react for you, plus all the other factors. You may not like as much as I did or you may like it even more. (If you have less than average revs, you may be happier with a PK 18 cover on a core that flares more than this one, for more overall hook. If you have average or greater revs, and do not need to see eveyr ball you own cover all 40 boards every time you throw it, you may enjoy this ball's hitting power. Sneaky strong is the best way to put it).
The cover, PK 18, is the most durable over the past 10 years, as far as I know. It is easy to return to good performance, as has been documented many times, mostly in the Brunswick forum.
(Talking about it makes me want to go to Ebay and see if I can find another 15 lb, as I sold mine a while back. Still have the 16 lb one.)
