What is the point of upgrading your pipes to higher tier pipes? (i.e. iron to steel) The only difference I have seen is the longer underground pipe distance.

they have more health and stuff...

The different pipes were originally mostly added to give variety to recipes, but then people wanted to be able to place them in the world too. I tried to make them different with different capacities on some pipes, but large pipes just slow down the flow, and small pipes cause sloshing, so in the end I set them all to the same size.

Basically, the only real difference is longer underground pipes, just use whatever material you have more of, or whatever colour you prefer.

Thanks for this answer. I knew I read this somewhere. Thanks for the confirmation.