What do you recommend for the groom's mic, an omni or cardioid?

For sure omni. You want to do your best to get audio from the priest and bride as well. A directional mic wouldn't be the way to go.

I saw the link there and it made me curious that perhaps there was a better way.

I'm getting some H2s and GSs and am very excited to stop using wireless.

You going with Seinheisser???

Fantastic mics....hurt the pocket a bit though.

Actually Zoom H2s and Giant Squids (GSs)