Custom woodworking forum?? I better leave.

Either will work. The key to making it last more than a couple years is to prime with Bullseye123 oil based primer(2 coats) on every surface. In fact, lay out the pieces and cut so all that needs done is assembly. Put on the primer and two coats of a good latex exterior enamel.

Then assemble and paint the screw/nail heads.

Thank you for your advice. Much appreciated.

Pressure treated wood will last longer in an outdoor application like this, even if you plan on painting.

The major water entry point remains end grain.
If you want the gate to last longer saturate all the end grain pieces with Minwax Wood Hardener.

Just dip each end of every board into the hardener and allot it to dry.

If it soaks in almost instantly repeat dipping after the material dries (not very long on a warm day).

The hardener will fill up the passages in the wood that allow water to easily soak in and start expansion and contraction cycles leading to checking.
If you use PT wood at least rot will take a lot longer.

Turns out the posts are out of plumb and also need to be replaced. I need to remove old concrete and fill the hole up with new concrete. This project just gets better and better.

I was thinking since I am replacing the posts, I found this company that sells a system where you set the posts in a pvc sleeve and keeps it from rotting and water damage. The other thing I like is if you need to replace the post you just pull out of sleeve. It gets embedded in concrete. Has anyone used anything like this,what do you think?