I would echo Alder adder's post and I dont think you can go wrong with either one. I happen to use RST and a hunting partner likes Poly Wad's Vintagers.
I realize you are not looking for 16 ga ammo, but below are comparisons for the two manufacturers according to a post revdocdrew made last December from the 16 ga site. I believe the information came directly from the manufacturers in response to a survey someone on the 16 ga site was making.
According to that post for a 16 ga 1 oz load the RST shells were a little slower at 1145 fps vs Poly Wad's Spred-R @ 1200 fps, but the RST also stated their pressure at 7600 vs Poly Wad's 9000. The 16 ga Poly Wad Vintager 7/8 oz load was stated to be 1200 fps at a pressure of 6500.
If you call RST on the phone 570-553-1651 they will tell you the exact pressures for any shell they manufacturer, and I believe they also test in house and have an outside party test their loads. They say the paper shells have lower pressure.
I am sure Poly Wad will give you the same information.
