Don’t look at the guage look at the gun. Does it fit, does it feel good and can you shoot with it.
For most normal ranges you don’t need massive loads of large shot, 21, 24 or 28grams is more than enough provided you can shoot straight. Even 9grams out of a 410 will kill just as well, but you have a much smaller pattern.
You need to think steel. There are lots of options in 12, a good number in 20 but 16 and 28 there are one or two options but this will grow.
Which is better - one trigger or two, and barrels stacked vertically or horizontally.
The only real option is to have one of each type in each guage and do lots of testing- but I doubt you will come up with an answer.