small foil wrapped cup is the best ratio - the right amount of chocolate to the right amount of PB.

The regular sized cup is slightly worse - the chocolate per PB is reduced.

Eggs are similar to the regular cup.

King Size (4 cups) are slightly smaller per cup, making them a little better than the two-cup package variety.

I'll have to pay more attention to chocolate quality, melt factor, etc. Really haven't noticed the difference you're describing, but I don't doubt you.