Just pattern both of them against something stiffer than paper (I use cardboard stapled to plywood) and compare penetration in addition to patterns
In a 20 the pellet count of 5s just isn’t confidence inspiring unless you are really going to limit your range
TSS 9s in your 20 will produce patterns infinitely better than what was considered good (to those who actually patterned) from a 12ga not too long ago.
