I have both and I prefer the Tiles.
99.9% of the time the network doesn’t matter because the item isn’t lost, I just don’t remember where I left it, and it’s either in range or wherever Tile shows the last known location to be. And even if it is lost, Tile app remembers it as being at the last place where I had it and my phone, which is practically always where I left it.
Airtag surely has better coverage, since like 50% of phones are helping, but the one time I actually lost something Tile found it. Someone had moved it so the location must have been uploaded by another Tile user. I use my Tiles daily to find my AirPods or a key set, I’ve used it once in years to find that (my Airpods case) when it fell out of my pocket in a park.
Tile is louder and easier to hear. Tile has several form factors, Airtag only has one, and honestly, any tile form factor is better than Airtags. I swear they picked the worst possible shape for it, it just has to make whatever you put it in bulge. You have to buy some sort of case to even use it most of the time, whereas a Tile can pop directly onto your key ring.
Airtag can’t ring my phone. I do that frequently.
I’ve used both extensively, I’ll keep buying Tiles. Or maybe one of these newer ones. I’d go so far as to say Airtag is only better at finding something that’s been stolen, and that’s just a tiny percent of the use cases. Tile is better in every other way.