I have heard good things about the Bounty,keeps pins low,and the Grand Illusion.

The playmaker is awfully snappy, or at least in my case it was. I'd strongly suggest the Hy-Road, the ball is very controllable, and I haven't found anyone in my area that doesn't like it for mediums and house shots.
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http://www.absolutebowling.com

Can't go wrong with the HyRoad's hybrid coverstock or the Grand Illsuion's polished solid coverstock
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My Arsenal:
Bounty(4.5 x 4.75 Fresh 1000 Abralon)
Twisted Fury(5 x 4 500 Abralon + Reacta Shine)
Raw Hammer Pain(Leverage 1000 Abralon)
Blue Vibe(5 x 5 4000 Abralon + Reacta Shine)

For medium volume, medium length conditions, it's basically going to come down to what reaction shape you tend to like.

If you want a smoother, more rounded breakpoint, the Grand Illusion is a very underrated ball.  If you want something a little more angular, the Hy-Road is a fantastic piece, and very versatile.  The great thing about both of these balls is they're not very expensive and have medium RG cores, but fairly strong coverstocks that are polished out-of-the-box.  They should work well even as the lanes start to carry down and then dry out.

I would not recommend the Pin Slasher for truly medium lanes -- it's just too strong in my opinion.  However, if you are seeing a little heavier volume conditions, it's a phenomenal ball!