Well, I'd say both, but for strict item transport I prefer Buildcraft, I use RP2 when I need a routing system. For item transport you also can't forget about RC, which offers IMO the most fun way of doing it, specially now with addition of locomotives. I tend to use different systems even in one build, just what seems more fun to do. Some subjective advantages of different systems:
BC:
- simple, both to craft and use. I prefer to build more complicated systems with simpler parts.
- machines can decide where to put input from pipes, which is impossible with tubes, tubes need sided inventory.
- better overflow mechanics (as I said, this is subjective opinion), I really don't like debugging where and why my system is stuck.
- gates, which allows for great control of automatic systems, they are very useful even in RP2 heavy systems, to for example control timer which powers RP2 extraction. Wires allow for good control without additional hiding of RS wires.
- a lot easier to split given materials between different paths in what average rate you want.
- it runs on constant RS signal, not on pulses.
RP2:
- They are a lot better when you need precise control, specially with RS. Both engines and autarchic gates are terrible at good control with RS, but Redstone energy cells makes it a bit better. However travelling item detection via gate condition is still terrible.
- They will route your items to where they can go, combined with colored tubes it allows for more complex systems without pipe hell and a lot of diamond pipe configuring. Sortron adds additional level of possibilities.
- They are necessary when you want to use transport system on frames.
- Machines look and work really well.
RC:
- You have actual moving carts with your items, which alone makes it vast superior than BC and RP2 item transports.
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