PAX Pokemon League

I'm having a bit of trouble deciding which ability I want to breed onto a Golurk. I can see the benefits of each one, and have a moves picked out for each one. I'll probably end up breeding both in the end, but since I don't have the best Dittos to breed with, I'm focusing on just one to start with.

[upnp]Iron Fist[/upnp]- Ups punching, mainly STAB Shadow Punch. Easy to get since it's a standard ability. Since Earthquake is also a good STAB move, is it worth having both STAB moves for coverage?
[upnp]No Guard[/upnp]- No miss Dynamic Punch. EV trained right, it could serve as a good tank (?) able to take any moves that hit it due to NG. Sadly, I can't seem to get my hands on one so far.

What's been everyone's track record/experiences with each ability?

I have only ever used him on an Iron fist team. Here's the set I ran with the team having a 33% success rate.
[spoilerf05]Golurk @ Assault Vest
Ability: Iron Fist
Level: 50
EVs: 252 HP / 4 Atk / 252 Def
Impish Nature
- Earthquake
- Drain Punch
- Shadow Punch
- Thunder/Fire/Ice Punch[/spoilerf05]
Bulky defense to offset the slowness. Shadow Punch and Earthquake are your go to moves, Drain Punch for a bit of recovery, and pick an elemental punch for coverage. There's really not much else to say. Its not ground breaking in any way aside from being the only Pokémon who's Shadow Punch benefits from STAB and Iron Fist.

I've got some no guard variants lurking around

It's the ability I vastly prefer, it's unlikely an opponent runs high-risk moves that would abuse the no guard ability-or if any that would that threaten golurk he's probably going to want to switch out for that anyhow. DynamicPunch is a beast of a move, and puts a lot of pressure on your opponent with confusion.

Really depends on your team comp. One of each doesn't hurt, they both have slightly unique purposes. It is also worth it to mention that you get perfect accuracy Stone Edges with No Guard as well, which can help a lot depending on the tier you use it in. I am slightly more in favor of the Iron Fist variant since you bring more to the table movepool wise.