I have "spare" sponge filters set up in my 2 bigger tanks, 60 & 69 gal. They are there in case I need to set up a hospital tank in a hurry so they are already biologically ready to go.
The 69 gal has a hydrosponge 3, but I put a basic powerhead on the lift tube. Works well too, and its quiet.
The one on the 60 gal has a lift tube with air bubbler, hydrosponge 3. It moves the water well ( you can see it chugging along when I do a water change). Downside for me is that it is noisey, this tank is in the living room at present.
I plan on replacing the bubbler with a powerhead.
If you are going to use the sponges on fry tanks, you could probably control the water flow better with the air bubbler.
