There are no guarantees that they will match up to your style - it's nice that your shop has some demo balls for you to try.
I tried the Creature S40 and didn't have much luck with it. Didn't surprise me since I didn't have any luck with the AMF Titan (same core) either.
The original Break (S70) is a top 5 ball for me. That ball just flat out worked for me. It was one of the few balls that I could use for all 3 league games with only minor adjustments.
The Break Pearl was okay, but I never did figure it out. I think I just tend to do better with solid covers. It did have its moments, but I don't think I ever saw the right conditions for that ball.
I had a Link S30 that was also okay. It was a little too specific for my needs. I bought it used and only plugged the thumb, so I guess I can blame the layout. Probably would have been a little more forgiving with a different layout. Worked great when I could consistently hit my mark (but honestly, that isn't very often for me!)
I still have a Break S75, Maniac, and Lunatic sitting around. For me the Break S70 was just that good of a ball that I never really needed to look at anything else. I got a 1/2 season out of it the first year, a full season the next, and almost a full season the following year (only stopped using it because I moved up in weight). I never had any problems with it - a couple of hot water baths and/or a resurface whenever it started looking a little lifeless and it was as good as new. I still carry it as my bail out ball, but I should probably just get a Break Out.