Early game, I don't use trains either, I just spaghetti yellow belt around! I even run long belt lines to the first ring of mining outposts. It usually only costs ~500-1000 belt to do so, which sounds like a lot but really isn't much.
Advantage of yellow belt:
- Don't consume power
- Don't produce pollution ( don't attract bugs )
- Are cheap. Rails themselves aren't too bad, costing only slighty more per tile than belts. But rails need stations, signals, chests, inserters for loading / unloading. Often combinators too. All add up to much higher investment, and critically in the early game, add up to more pollution produced before the pay-off of improved resources incoming.
- Don't need lots of belt for the stations. A typical loading/unloading station can often have so much belt for "efficient" (fast) loading/unloading that you could have belt half your way to where you're going just laying that belt in a straight line.
If you're going further than the first ring of extra resources, then trains are amazing, but there are more than enough resources several times over in the first ring of resources to get a rocket launched. The first expansion ring tends to have 500k-1Mil per patch, and have several patches, so there's no need to go miles out pre-rocket.
It takes surprisingly little raw resources to actually launch a rocket. Someone did the maths once and calculated completing the game as needing a minimum of ~500k Iron ore. At 15/s, a single yellow belt can deliver that in under 10 hours, way below the time of a typical playthrough. This technically means a single smelting line is all you need to actually complete the game still in a reasonable time. Of course, trying to do so from a single lane would be extremely painful, and need a lot of attention to preventing over-production of intermediates, especially when it's much easier to make a few smelting lanes. I'm not recommending that, but I am recommending just slapping down new lanes and production wherever you feel like it and whenever you need, rather than pre-planning 4-lanes of plates that aren't actually useful of efficient.
Unless you mean your "main bus" is just 1x copper and 2x iron lane, in which case fair enough, but when I attack the concept of the bus, that's not what I'm railing against. What I'm railing against is the design pattern where people put down 4 lots of 4-wide lanes to bus far more iron, copper and intermediates than will ever be needed to actually launch a rocket.
Busses aren't efficient by any metric, other than minimising personality, creativity and thinking.
With a bus you just follow the same template done before, it'll get you to the end, but it teaches bad habits and isn't efficient. It isn't quick either, you'll spend a long time putting down lanes and splitters and undergrounds. All of which need producing.
For late-game (post-rocket), then either a bus design or train / city-block designs can work well. I prefer trains, but large busses have their place for mega-bases.
But for pre-rocket, or anyone starting out, spaghetti is absolutely the way to go. It'll also better teach you via your own mistakes.