Back in my day we had one size of card and we liked it. 2 1/2 x 3 1/2 and a 9 pocket page is all you needed.
Now days we have cards between 20 pt and 180 pt thick requiring a bunch of different sizes of toploaders. Topps, Panini and UD jerseys are generally 75 pt, Topps, UD and Panini patches run 100 to 120 pt (BCW make perfect sized toploaders for patches) and sweet spot run 180 pt for the helmets and such. Quite a few UD jerseys are 55pt however. God knows what those UD Bug cards are considered. And as far as size we have all sorts of shapes and sizes. I remember the fits we had when 1989 Bowman came out and they were bigger than the normal size and I had to go find plastic sheets for those.
Lately I had decided to go ahead and build my Mayo mini and Murad mini sets. Knowing that there are those 15, 12 and 9 pocket pages out there I set out to finally put them in pages. I found a box of 100 15 pocket pages for $16 shipped and awaited their arrival. They finally came and I set out to sheet up my Mayos.
They are about 1/16 too wide. Ugh! The Goodwin mini on the left fits fine:
So with my disappointment firmly in place, I did what I do. Set out to find a solution. I then went to look at the 12 page pockets. While discussing this with Duane from Democratic Roadkill, he inquired as to whether those Goudey Mini's would fit. Too tough to tell without having the sheets. Looking on Ebay, I noticed that sheets with shipping were ridiculous and I didn't want to bet $20 on it. So I swung by Heaven Sent cards in Tualatin, Oregon on my way home from work and picked some up and 4/$1. The shop owner was nice enough to dig out some mayo and murad stuff to try out. Seeing that the Murads would be close, I bought 20 and headed on my way. A few minutes ago I gave it a try and these are the results.
Admittidly these sheets are for stickers so I was taking a chance. The Mayos are way too tall, the Murads are close but you may find the tops of the cards exposed and these are not a long term solution for them, and the Goudey minis are a big whiffa. So essentially these 12 page pockets are a waste.
The upshot is you should just stick with the 9 pockets for all cards but Goodwin and Ginter Minis. For those the 15 pockets will work. The problem is that the smaller the card, the more likely the cards will slip out. The fix for this is to use penny sleeves. Yup, put the mini in a penny sleeve and then in a 9 pocket page. The only other storage possibility is to use those tobacco top loaders but I determined this to be unwieldy to store sets.