Faster belts have higher throughput. If you use a belt to e.g. feed 30 smelters, you need to transport enough ore and coal per second to keep the smelters fed. With a yellow belt, you'll find that around 20 smelters will be able to empty out a single yellow belt. So, if you want to have more ...

Hi everyone,

I've played Factorio now for a couple of hours (like 50 or something) so I haven't seen everything yet. But you develop those faster transport belts very early and I still only use the slowest ones.
Mathematically it doesn't make any difference for transporting stuff which belt is use ...