[Closed] Drive train advice x 2

Right need to replace two quite different drive trains

One is on my good bike (Cotic Soul for interest, not that it matters)
After reliability and light weight. Thinking XT cassette, Sram pc991 chain but unsure re chain rings - Middleburn? or Blackspire? Don't want to spring to XTR style costs but want somethign that will last longer than swiss cheese.

The other is for my commuter - a much abused and neglected bike. Here I want CHEAP and durable. Can be as heavy as sin. What will last longest with zero care and costs next to nothing?

Both are 3X9 setups.

Thanks!