We had a home built about five years ago. Our deck is constructed with pressure treated wood and while it is under a roofed area, it has south exposure and gets quite a bit of sun. Our builder did a couple of things that appear to have paid off:
1) Suggested we not treat it with anything for at least six months. He wanted to let the moisture bleed out of wood via exposure to sunlight before treatment.
2) He gently steered us away from Thompson's. He admitted it was partly an appearance thing, but he preferred Olympic Water Guard. He also thought Olympic had more staying power. He said to plan on washing and retreating about every other year. However, based on your comment you might not want to use Olympic because it does add an amber tone to the wood.
We followed his advice and are pleased. At the end of six months the deck had sun bleached slightly. I cleaned and sprayed two coats of Olympic which gave it a slightly amber look. Both of my subsequent retreatments were preceeded with a light pressure wash using deck cleaner. These subsequent treatments were done with a brush (one coat), which I believe does a better job than spray. Again, the deck will retain a golden brown appearance which you might find objectionable.
By comparison, I built a deck at a previous residence and used Thompson's. I can't say that Thompson's provided a bad finish but it added absolutely no color to the wood. It was like brushing water on - at times it was difficult to tell where you had treated. We sold the house before we could see how it aged. As far as cost goes, they are both in the same ballpark. I belive Thompson's has been running a "5th quart free" sale for the past
3-4 years - Still talking about $12-14 dollars for a 5 quart can.