I think you need a mixed fleet for economy of effort.
To use a 737, C130 and other big iron is nice, but you need a dedicated water supply, pumps and mixing tanks capable of refilling the aircraft quickly and there aren’t going to be many of these necessarily near a fire and they are rather a blunt instrument compared to a SEAT or a helicopter with a bucket.
I fought one fire last year which luckily was only about 8km from the regional base and also luckily three SEATS were available.
They set up a circuit so we got a drop about every ten minutes and they controlled one inaccessible flank of the fire, leaving us to deal with the other one. A B737 or C130 would have been overkill and probably not very effective as this fire was on a hillside where access was difficult and you needed to confirm it was out by stages. The smaller aircraft controlled by the spotter helicopter was able to target the drops very precisely which meant we didn’t have to run and hide all the time because the drops could be synchronised with our work rate, it all worked out quite well.
Later we had the Myhree fire where there was a lot of forested ridgetops burning and the potential of losing a lot of the King valley grape harvest due to smoke taint. The C130’s did a great job on the main fire fronts which were large and inaccessible. All we had to do was watch the edges and look out for spotting.