I think it's interesting that a big dick is beating out even money on the value scale.
I've never had either of the options listed, so I can't really compare the two. I know that if I had money I would still get laid, even if the woman wouldn't enjoy it, so I'm kind of leaning towards money. A big dick would be great, probably better than great, but the restrictions given by the OP mean I could never use the big dick in a money making capacity. As much fun as I could have from a big dick, I think I could have more fun with money.
If I'm rich, at the very least I could use my money to create a dick shrinking drug and distribute it in the water supply, making everyone's dick as small as mine. I think that particular act of revenge would make up for my own lack of size.