Well, in my opinion, they will both last the same time. 12 to 15 years.
They will with time, in Texas 6 months, turn grey with the heat and rain. Sprinkler systems will prematurely make the wood stain faster and with a different color. The staining will take the shape of a fan from the nearest head. This is due to the stuff in the water, flouride, clorine, and all that stuff.
Preservatives will only make the color look newer, but both are adapted to anti, rot and insect invasions.
Now, remember this is only temp, cedar looks better new, Wolmanized looks blah, but they will both look the same after weathering.
Go with the Wolmanized if on a budget, if not, heck with it go cedar.
Steve Ps, do not attempt to seal or stain Wolmanized wood until it had thoroughly dried out with the summer heat. When new it has so much fluid and chemicals in it that it leaches the stuff. Hit it with a hammer and chemicals splatter.