Wedding ain't a cosplay party.
Groom/bride can dress whatever the fuck they want but they won't have complete control over the guests. What you gonna do when your rich uncle Joe shows up in overall with a hat? Turn him away? Pfft.
In less than two pages we've already had plenty of differing opinions, so I would say there's really no definitive right or wrong answer to this. It's your wedding - wear what you like the most.
However, bear in mind that the whole of Styleforum will disown you if you make the wrong choice. We are watching you.
Slightly off topic - as a Brit I'm always fascinated with the (seemingly exclusively) American obsession with social 'rules'. People throw them around on these forums as if they're gospel. I struggle to get my head around them sometimes - my favourite is always the strange social hierarchy that dictates if you are deemed worthy enough to wear french cuffs. Very strange.
The tradition is that the bride should stand out, its "her day" etc. The groom is simply supposed to foil to make her look good and at most that they look like a good couple. Obviously after the wedding its a life of servitude for the wife ;)
Look at any traditionally semi-formal event and men pretty much have a uniform to wear - morning dress for weddings, garden parties, races, black tie for "party" type evening events and white tie for formal balls etc. Women on the other hand for all of them have an almost free hand other than potentially whats allowed to be revealed/ requirement for a hat
If you look at many photos of weddings the groom and groomsmen are all dressed identically or a moderately minor difference like the colour of the grooms waistcoat.
I repeat however, its your wedding though and if you want to wear a purple onesie and a green top hat then thats your choice