I assume you're pointing toward the 1Ghz Dual Core processor as opposed to the 1.4Ghz Quad of its bigger brother.
Personally I don't see the problem. It's taken everything I've thrown at it, not a hint of any slowdown. And for the 5mp camera opposed to the 8mp of the normal S3, It's just a non issue for someone who has a dedicated camera anyway.
Only other big differences are the screen res and 4G...but damn, screen looks good from where I'm sitting and 4G doesn't bother me too much since I live in the sticks anyway.
I just didn't see the justice in an extra £130 for the normal S3 to be honest, plus it's very big. I like to text with one hand