Pressure treated lumber has always been my choice for exterior framing; period. It also winds up being my choice for decking for 2 reasons: lasts (virtually) forever...and...is the most affordable option.
Some notes on PT lumber.
I don't know the specific percentages of vendor compliancy or specifically when the change(s) occurred, but current PT from home centers is arsenic free. The old PT (maybe 8 - 10 years ago...?) was not. We have had some discussions within this forum regarding the potential of toxicity within a pond, particularly for the old stuff. As I recall, we wound up with no certifiable scientific evidence to point to yea or nay. Also, if it is the old stuff, you will definitely need to wear a face mask during cutting to eliminate the potential of breathing the dust particulate. Personally, I have built many decks in my younger years with "the old stuff" and never wore face protection. I'm still here typing...b'pamZ:Lfm:.........
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(kidding)
Also, the correct fasteners for the new PT is stainless. You can "get away" with galvanized, but it will react with the copper chromate (?) preservative and will eventually corrode.
