I've got 2 Angers. One drilled 3 3/8" stacked leverage @ 500 grit, the other drilled semi-Rico, highly polished.

I've also done this with two BW Bites. One could start the night dulled up, the other slightly polished to follow after.

IMO, there can be alot of benefit from this.
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Nothing Hit's Like A Hammer

I take it to the extreme. I have 3 SD-73's set up with different drills. One is leveraged with pin at 2:00 cg stacked below 3 3/8x3 3/8, one drilled Rico and one drilled 6 in pin above middle finger cg kicked out at 30 degrees.
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my vote for president is green nikes

In have 3 Gravity's and 2 Codes all box surface but with different drillings. Gravity's #1 and 2 are set up to compliment one another with Gravity #2 going a couple of feet farther down the lane with the same breakpoint shape as number 1. #3 Gravity is flip leverage. Codes are drilled with one 4 1/2 x 4 pin under and the other is 5 x 3 1/2 pin up

I have two old Ebonite Crossfires, one pin in and one pin out. The pin in ball is drilled with the pin to the right and down from my ring finger, the pin out ball is drilled with the pin to the right but about 4" up from my ring finger. CG slightly to the right on both (in case CGMADUR).

The pin in ball goes a little bit longer but stronger off the break point, just enough to see the difference. I can tell but lots of folks cannot.

I mostly keep the pin in ball as a backup in case the other one breaks, cracks or wears out. They work great on THS with flying back ends.
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Never take a sleeping pill and a laxative on the same night.

well I re drilled a ball to Rico. I believe it use to have a pretty strong layout since it was a big hooking ball for me. Now with the rico drill it's pretty straight with a slight hook. If you're thinking about doing this, maybe dull the stronger ball and polish the weaker drilling.
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Brunswick Scorchin' Inferno (retired)
Roto Grip RS-P (HIGH Game 269) / now using as spare ball/ dry lanes
Ebonite RSX300 (HIGH Series 650) / Now Rico Drilled
Hammer Cherry Vibe
RotoGrip Cell x2

I've bought multiples of the same ball and had some great success.  

I've done this both ways.  I've drilled up two of the same ball and put different layouts on them for a nice 1-2 punch.

I've also drilled up two of the same ball and used the same exact layout but changed the cover grit with awesome success.  I prefer to use the same layout and just change the cover grit.  I prefer this approach because it gives you the same type of reaction shape and either more or less length.

I remember a league session when I had two Blue Vibes in my bag with the same exact layout but different cover grits.  One was 1000 grit and the other was box.  I was using the 1000 grit BV and moving left as the pattern was breaking down.  Everything was going great until I got to the 4th arrow with 10 at the breakpoint.  Once I got to the 4th arrow I started leaving 10 pins.  There were some other bowlers on my pair that started off playing deep and blew up the inside.  So I switched to my box covered Blue Vibe and moved back to the 3rd arrow out to 10 at the breakpoint and started carrying all 10 again.

I am a big believer in drilling multiples of the same ball.  For me buying bowling balls is a crap shoot.  Nothing worse than spending 200.00 only to find the ball doesn't match your game well.  If I find a ball that works well for me, I just buy multiples of that ball.  You can realistically build an arsenal out of multiples of the same ball and just change the cover and or drill layouts between them.

I've also found thru my experiments that even the so called light oil balls can be used on much heavier conditions with the correct surface grit.  I've knocked the polish off pearlized bowling balls only to find they handle a ton of oil and can be used on a lot of different conditions.  I've been doing this for years.

Six Pack: I would use the same exact layout and just change the cover grit.  If you use two of the same ball but change the layout you may end up with such a drastically different reaction between them that it's just like using a different ball.