Lumper, I do not think that shotgun porting is effective. There just isn't enough pressure generated by the ammunition to allow the effect of bleeding a little of it off prematurely to be very noticeable. Many years ago, my son and I shot identical KS-5s - his was ported and mine was not and neither of us could tell any difference. Now, on rifles where the chamber pressure is six to eight times that of a shotgun, it really does reduce felt recoil.
Since porting is something that can always be done later if you want it, I'd buy an non-ported gun because porting unfortunately cannot be undone. About all I think it's good for on a shotgun is making more noise and your gun and your squadmates dirtier. Others will disagree with me, but I'll bet most of them bought a gun that was already ported and are simply defending something they own.
I would get the trap model because - for me, anyway - it is easier to adjust to shooting a slightly higher-shooting gun on flat targets than it is to adjust to covering every trap target with the muzzle of a flatter-shooting gun. I own one shotgun that is not a trap model - an 1100 synthetic field - and every time I take it hunting, I have to adjust to not shooting just under my target. But again, that's MY preference.
The adjustable comb is up to you, of course, but I think every production target shotgun stock should have one. There is an excellent stock smith about 50 miles from me, so I'd go with a Monte Carlo stock and have him make it adjustable if I were buying an 85TSS because I don't think SKB offers an adjustable comb on their Monte Carlo stocks.
The gun I tested had a straight stock with a factory adjustable comb. The rear adjustment post was installed in the stock off-center to the left, so if you put both posts on the same alignment mark, the comb was not over as far at the rear as it was at the front (from a right-hander's perspective). I'm sure that is not typical for the gun.
My test gun was a brand-new non-ported 85TSS combo that a friend of mine purchased to replace one he had before and regretted selling. I buy many of the guns I test, but I had to return that one to its owner.
If you decide upon a trap version, I would suggest that you then consider spending the extra money for a combo. If you ever want a single barrel for trapshooting, you'll be glad you bought the combo because SKB does not sell barrels separately.
There are several 85TSS trap guns around here and all their owners like them a lot.
Ed