-Seed beads: Good and bad. With steel: murder. With lead: alright. Seed beads shattering in itty bitty pieces can kill bags. Reserve for only strong facile colors (color choices that you are confident in knowing that they won't bust holes too quickly).
-Lead: It's alright. It has its applications. I have a nephew and niece that are just kids, and I have a dog. I don't want them exposed to lead, so I don't use it much. I think of it as a "soft" filler. Good with seed beads. Kind of sucks for everything else. Plastic pellets is a maybe if you make the ratio good.
-Steel: I use it all the time. Zinc-plated steel shot is the most versatile you can have. However, it can easily rust if: 1)you sweat on your bag alot with this filler and never wash it and 2) you wash it but don't properly dry it. That's why people don't like using it. This is a "hard" filler. With seed beads, it will murder bags because of the density of the metal. With plastic pellets, the bag may seem a bit too full for a golf-ball sized 32. Everything else (like unique fills) make it super nice.
-Tungsten/bismuth: This fill is highly sought after. I don't need to talk about it. It's super dense, so I don't recommend seed beads with it, like steel shot. I think through washes and whatever, it can make your bags really dirty. It's non-toxic, so no worries. (That means you, Erik Chan.
-Planet footbag steel shot: I think this type of steel shot is the most versatile "support fill" in the market. It will work great with all types of filler. It also doesn't rust, so that's bonus. I really want to get more, maybe like 8 pounds of this stuff. If Freedom is selling, I'm buying. Yeyeah.
edit: Btw, when will freedom have the planetfootbag fill in stock? I ask this because I have Alex Trenner on hold for a potential order I have at the moment, and I don't want to keep him waiting. Plus, I'll save on shipping if this is so, because I only want to buy this filler and a t-shirt from the pf shop.