My issue with the covers is that, in my experience, covers on Columbia-poured balls are some of the weakest in bowling (or, more accurately, covers on stuff that comes out of the Texas plant). The cover on my Evo, for instance, is pretty weak, as was everything I used to get from Columbia and AMF prior to the switchover to 900Global.
I can't remember whether Columbia or 900G poured the XP, but it still came out of that same plant, so I'm pretty surprised by its reaction.
I'm not a huge Brunswick fan at all, but for my game, Brunswick covers were a good match for most Lane #1 cores. The Bomb cores didn't work so well for me, but everything else did.
Jess