Ready Seal is it.
Ready Seal, in Sun Brite's opinion, is the best sealer because 1) it is a penatrating oil that alows the wood to expell any trapped moisture. 2) it is not a coating, so is won't wear away from traffic. 3) it is made with a parafinic oil base, not linseed oil, so it doesn't contain sugars and starches for mildew to grow on. 4) It can be rained on in 10-15 after aplication and be walked through during aplication without harm. 5) It's incredibly easy to work with. 6) It not only provides superior water protection, but also supperior UV protection and comes in many colors. 7) It can be aplied in many ways (i.e. brush, spray, flat pad, roller, rag) This list is by far not complete, but I don't want to write a book to bore you with. I just feel it's too easy to say what's the best sealer with out really supporting it. I hope I've done that for you.
Tracy Handl
P.S. If you use Bleach in your cleaning procces (which is fine) don't forget to use a neutralizer/wood britner.