I like my ultra 20 over my 12 gauge slug gun for one really big reason, recoil. I can sit in a stand or from a bench rest and shoot 3" mag 20 gauge federal sabots and see the target move on impact. With a 12 gauge I'm not seeing much of anything for a second or three after I pull the trigger on a 12 gauge 3" mag slug.
So, in the end, knowing I'm not getting kicked by a mule I shoot better/more accurately. So while their is probably no inherent difference in accuracy of the 12 and 20 gauge H&R slug guns (tracker or ultra) there may be a mental difference in the shooter that makes the 20 more accurate.
Also, if you bought a .410 - 12 gauge pardner you can put either the 12 or 20 gauge tracker (iron sight) barrel on it, or the 20 gauge ultra barrel. The 12 gauge ultra barrel only fits on the 10 gauge shotgun frame. The 20 gauge ultra is a 12 gauge barrel blank, untapered, with a 20 gauge bore drilled through it. The 12 gauge ultra is the 10 gauge barrel with a 12 gauge bore drilled through it.
The tracker barrels are much lighter, not tapped for a scope, and are considered by many to ba carry slug guns because they are so light. And because of the light weight also have much more recoil than their heavier obiese ultra brothers. Which come with a scope mount but no iron sights. Most consider the ultra as a stand/poster gun because of the weight.
I hope this helps.
later,
scruffy