Are you an owner of a .45 M10? If not, are you looking to buy a M10, but you mostly want to shoot 9mm? To me, there are three ways to shoot 9mm from a factory style upper. In ascending order would be M10 .45 with the 9mm adapter, 9mm mag catch, and the factory style 9mm mags. Next would be a M10/9 magwell receiver with factory style 9mm mags, and finally a M10 with the Uzi grip magwell conversion.
The modified MPL mags that were the original factory mags are currently very expensive. The last I knew, the market value of those magazines were $150 each. There are some knockoff magazines, but they are hit or miss for reliable feeding. I feel the Uzi magwell conversion is the best for 9mm, as the Uzi mag is double stack, double feed, robust, and very inexpensive. There are .45 caliber Uzi mags, but they are lower capacity, if you want to fire .45 in the Uzi magwell conversion.
Just set-up an M10/45 in 9mm for a friend. Just purchased a complete 9mm upper & bolt, magwell adapter, made a custom mag catch, and some 36 round (what I think were RPB) double stack double feed mags.
Everything went well except for the magazine catch. The M10/9mm catch did not work in this gun as the metal thickness of the grip plus the insert did not allow for the catch to reach the magazine. (A M10/9 would not have had the extra thickness of the magwell adapter.) After making a custom mag catch the gun was 100% in 9mm.
I have run 9mm in my M10/45 for years, mainly because 9mm ammo is usually a lot less expensive than 45acp ammo.
I use the drop in kits listed above. I always use the 9mm mag catch because for me the 45acp mag catch doesnt work well with the 9mm mags. However, years ago on this forum there were threads about using 9mm kits in 45acp guns and a lot of guys here were able to use their 45 mag catches with no issues on 9mm mags so maybe it is just depending upon your particular weapon.