There is a huge variety of slugs these days to choose from. It pays divedends to get a variety of samples and see which one is the most accurate out of your particular shotgun. Shottys tend to favor a particular brand or style from gun to gun regardless of make and model of that particular shotgun.
Your running a smoothbore so you'll want to stick with rifled slugs or slugs marked for use in smoothbores. That excludes the vast majority of Sabot Slugs.
Brennekes have an excellent reputation for accuracy and knockdown power so I would start there. Get a box of Winchester's flavors and Remingtons and Federals and all the usual suspects and log your results.
That's really the best way to see which one works for your particular shotgun.
I hope that helps.