Favourite urethane I ever owned was a toss-up between a Magnum 10 and an Ebonite Gyro 1, I had a great deal of success with both of those pieces of equipment and, found it suited my "down and in" style of shot quite well.
My Favourite Resin ball of all time, thus far, would have to be the old Nitro R2.
I swapped this ball off of Norm Green for a packet of Horizon 50's cigarettes when he quit bowling a few years ago, he'd only bowled about 150-games with it when he gave it to me.
The Ball has had about 1400+ games on it now, and unfortunately seems to be dying in the ass a bit, but I've shot almost all of my personal best scores and averages with this one ball.
It was perfect for me, and, I'm yet to find anything since that matches up quite as good.
And it was my 300 ball, so it always will be my favourite.