I can speak from both angles. I have used bleach to clean decks with great results. One thing I notice is that bleaching a deck tends to raise more grain than say Wolman's or other products that don't contain bleach. Also, I see a difference in the color of the wood whan it dries, a bleached deck seems almost white compared to the more natural look a wood brightener leaves. So after 6 years of doing it both ways I say this....I prefer a wood brightener at higher cost but to me it does a better job. But I did vote sometimes because there are still some occasions where I use bleach on decks. It is a very powerful weapon against mildew. If a deck has a goos finish but is just mildewed, I will downstream bleach then rinse. Clean as a whistle. If I am doing a maintenance coat I may use bleach just to kill any mildew that may be on the surface. Bare wood, I almost always use a brightener to clean for a more natural look.

Mike's Powerwashing