I'm like you, dude -- if my girl (or guy) had pics of an ex's cock, I'd want to see them. I want to know what I'm up against, even if only to obsess about it and feel hopeless that I'm smaller. And it's not at all that I want humiliation -- I WISH I had the biggest dick out there, but I can't help wonder what else my sf has had. It's just the way my brain is wired.
Now, as for my comparison of the two, I like yours a bit better. He has the size advantage, but his long enough that he looks a bit skinny, which I don't like. Even if he's technically thicker, the appearance is skinny. I also like that he's uncut, but that only barely matters to me. I usually like veins, but his look weird.
Yours, however, just looks like a little better dick (no pun intended). It's more proportionate, your head looks hot, and it looks like it would be more fun to play with. And don't get me wrong, I give too much weight to size most of the time, but something about your dick is very unique in a really-turns-me-on kind of way. In fact, I'm going to pull your picture up again now and have a spank. Fuck her good tonight!