My reason for going cordless was a little different, but I do agree with what Fred says. Knowing particularly in this case of a possible performance concern with cordless in PT, unless you have a reason for wanting cordless over corded, corded will always be more powerful and typically cheaper, sometimes by a lot.
I’m rarely in a place where I couldn’t plug in a corded saw, but for me it is usually the convenience of not having to that makes me reach primarily for the cordless. I do have a corded one and it does get used as well, if I could only have one, it’d definitely be the corded. The few times I’ve needed the power I’ve been glad to have it. Ripping sheet goods, particularly in full 4’ or 8’ cuts, I like the cordless, because I don’t have to feed the cord over the edge of the workpiece, or have it drift along a side edge, which also wears on the cord. I also go help do projects at friends houses, some of whom don’t own a circular saw. Rather than figuring out which circuit they’ve got their high powered computers plugged into so I don’t plug into the same circuit with a 15 amp saw, or if we’re running a shop vac and/or sander from the same circuit at the same time, it’s just easier to take a cordless. Those applications though rarely involve PT or similar challenging materials, so I know my M18 saw will get the job done for those, and I have no qualms about leaving the corded at home. At Habitat projects, I’ve even used the little M12 circular in a pinch for cutting 4x4 PT fence posts to height (it takes at least two passes at its lacking depth and sometimes leaves a twig in the middle), and it got it done. I definitely could have used just the corded for all those and been plenty happy, but the grab and go and not worry about plugs or extension cords or where I’m plugging in was enough convenience to justify the price premium. Plus I was already on the Milwaukee platform, so have oodles of batteries.