Absolutely pressure treated because the treatment makes it highly insect resistant. Mr. Had a design build landscape firm for forty years.

The untreated pine will deteriorate much faster. Even then you should apply a water sealer to the deck once installed.

On edit: You can apply the sealer before but once you nail it down you would need to reapply because the nails will break through the sealant.

my son talked me into cedar for my new deck/porch 2 years ago and I am happy with it


https://www.familyhandyman.com/decks/comparing-deck-wood-cedar-pressure-treated-wood-composite-decking/view-all/

My daughter and I just ripped off 25-year old pressure treated boards from our deck and replaced it with cedar.

I had been going back and forth trying to decide whether to use composite decking, but in the end chose cedar. It looks good, smells good, is rot-resistant and a whole lot easier to work with than PT.

The price was just about the same as composite and was very easy to install using that CAMO tool (no exposed screws).

After we stained and sealed it, it looks completely gorgeous!!!

(I do have a small complaint --- after a rain, the water just sits on top of the boards --- so we had to get a large sqeegee to push off the water).

We did our deck in regular pine and stained it every year. It had to be replaced in less than 10 years. It had not completely rotted but had bad areas with huge splinters and many of the boards had warped.

Spent the extra up front and glad I did. Never have had to paint or sand. The addition of stainless screws eliminated any possibility of rust also.

Would not hesitate to do it again, but probably never will in my lifetime. Could attach a photo if I knew how.

https://www.trex.com

I wanted a new look. It was still in good condition when I tore it out. In fact, I used many of the 2x6s for other projects.
For the new deck, I used the very best "pressure treated" lumber I could purchase at the big box store. It is already rotting(and yes, I used the best deck sealant I could buy). Good luck with your search, but just be aware that nothing last like it used to do.

Got pulled off the market cause it had arsenic in it. The new stuff is only good for half the life of the old stuff.

but the "shelf" life of the new stuff sucks big ones.

I'll echo the poster below. Well worth it.

At least here in Colorado. The sun is our greatest problem. A lot depends on your climate and humidity.
I would be inclined to replace with the same material that lasted 40 years and let the next owner deal with it when that time comes.

There are a number of ways you can choose to replace your deck. I would suggest you to go with the composite decking as it will give you desired flexibility. Also, if you want your backyard to look more elegant get a new furniture from any of the genuine furniture providers and make sure that you choose the best design furniture for your backyard. Last month, my cousin did the same by purchased a new design set of furniture from the official source at an affordable price and now his yard looks really amazing and comfortable too.