It's my understanding that the "quench pad" has a certain limit of effectiveness. It's goal obviously is to increase turbulence for complete combustion, preventing pooling or left-over fuel in the ring lands.
It's also supposed to increased octane tolerance... though I have my doubts about the effectiveness at that since quench doesn't really occur until you get under 0.065" or so and iginition has already been triggered.
From what I've read about big block piston design it is much better to have your quench-area be a solid ring along the outside of the piston than to have a solid pad on one side of the chamber. Why? A few reasons I'd guess, but the big one seems to be the effectiveness a quench "jet" has in mixing the combustion chamber when it's injected into the middle of the chamber (i.e. over a dished piston), than accross the bottom of the chamber (i.e. over the surface of a flat-top piston).
Mind you, this is just conjecture from some hot rodders and engine builders I'v talked to, but some of them are very knowledgable and one came pretty close to winning the Engine Master's Challege a few years back.
Main reason the small blocks use flat-tops (like the LT1's -5cc) is to get the compression ratio they want. Using a dished piston (i.e. JE -31cc uses in S/C engines) would require MUCH smaller combustion chambers in the heads (i.e. say 20cc instead of 58cc) and this leads to 2 issues:
1) valve angle probably has to be reduced if you wish to keep the valve sizes large (therefore heads and intake/exhaust manifolds must be redesigned), and
2) increased likelyhood of an interferance engine design. Not a major issue, but defintely not a step in the right direction in regards to reliability.