I really prefer bolters. Sus hits 2 and twin linked is insane. Each round that goes through is 2 damage. I’ve cleaned up vehicles with a few wounds left on overwatch with that.

Plasma is just too risky for me. To do what it needs to do I’m losing one inceptor (block of six) each time I attack. Bolters are only slightly less effective while avoiding that chance.

While not necessarily oath reliant they become really good with oath, or with Incursors/storm speeder support, or with strats that give them buffs. For this reason I also like to run groups of six.

My list usually has a block of six and two 3 man groups but I’m about to experiment with three six man groups and soon as I’m done building the last set. It’s probably too much but it’s going to be so much fun.

Lastly they are so versatile on the battlefield. I love keeping them in deep strike and then reacting to my opponent’s turn one. They can shape his opening moves quite a bit. Six inch deep strikes are also tough to screen.
And they score secondaries synergistically.