I've never dated a fellow vegetarian or vegan. Just one guy who was veg-curious and experimenting with it.
Most of the vegan guys I meet are younger and we don't end up having much in common. Not that I would rule someone out based on age, but in can be a factor in just not having the right kind of connection.
Now that I have some time to reflect, I wonder if I should look for a vegan/vegetarian/mostly plant-centric guy. My past relationships with omnivores have been marked by differences in basic values. It tends to extend beyond what to eat for dinner - taking responsibility for your health regardless of what other people think, doing what you believe is right regardless of what other people think, educating yourself, thinking critically, prioritizing animal welfare, caring about politics, and much more.
I want to find someone who shares those values even if they're not fully vegetarian or vegan.