Who is considered Tier 1 these days?   My instincts say Mesa but I haven't been keeping up.

I have a Esstac shell card on my Remington 870 and a Mesa Tactical shell carrier on my Benelli M4. If I had to only choose one, I'd choose the shell cards. The Mesa carriers are nice, but relatively bulky and do not secure the shells as well as the shell cards. It's kind of a love/hate thing when it comes to how well the shell cards secure the shells. It's MUCH easier to load and remove shells from the Mesa carrier, but if you shake it a certain way, shells can fall out.

Vang Comp

Can only speak to what I have. Esstac shell cards. They work well. I also carry a bunch of extra shell cards in 5.56 mag pouches on a chest rig. I carry about 50 or so shells if I remember correctly.

I've used them all. I'm partial to the esstac and vang comp velcro. Vang comps dont curve and i like the angled card, esstac i like the loop for grabbing them. I believe the current tier 1 option is  https://www.aridusindustries.com/products/remington-q-dc/ , this option will will set you back the most money.