Homeowner DIY deck repair. 20' PT with simple install vs 12' + 8' cedar staggered.

Hoping for a sanity check on this decision I have to make.

I'm preparing to replace the top boards on an 18' x 10' deck. The existing boards are PT.

I'm a relative novice in carpentry, so I was hoping I could just order some 18' PT boards from my local lumberyard and jump right into the work. When I got to the lumberyard, they recommended I use cedar boards instead. The pitch was pretty convincing, less checking, warping, movement, etc.

The issue is that would require that I go with a 12' + 8' staggered pattern. My lumber yard doesn't carry 20' cedar. This deck is a bit older, the joists aren't perfectly spaced (a sister joist is also in play), and I have stairs on each side of the deck preventing overhang. So I would need to be making more precise cuts and making sure I was ending on joists properly.

The alternative is 20' PT, which would only require a single cut and would avoid the extra joist complexity.

I feel like my options are to use the correct material with more complexity and risk of mistake or use a lesser material with a skill-appropriate complexity and less risk of mistake.

I'm compelled by the simple install. Any input would be super appreciated.