You are asking questions without providing enough information as to the decks condition, the climate, the kind of wear it gets and so forth.
The product chosen, whether clear sealer, semi-transparent stain or solid stain depends on appearance desired and you cannot really make an apples to oranges comparison without factoring that in somehow. And the material of the deck wears with exposure and not just the stain or sealer. What material you use can make a big difference in how the finish for it stands up. How the finish is applied and the surface prepped makes a huge difference also.
Any deck finish is going to require regular attention and maintenance. There are products that claim to last a long time but realistically you should plan on refinishing every 2-3 years. If you get more you will not be disappointed. If you are only getting a season under relatively common climate conditions you are using the wrong product.
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