What do I use?

Let me start by saying this site is awesome! I had no idea the crap I was buying at the big box stores. Anyway, I'm needing some advice on whether to use the twp 100 or 1500. They are both available here in NC and my deck is in the full sun all day everyday. I built on to the existing deck about 3-4 months ago. The older part is about 4-5 years old and did get a couple coats of cabot semi trans when it was new. I'm pretty sure that's worn off now as it has grayed some and has been pressure washed a few times so I think I should be fine skipping the stripping step, but I do plan to wash the entire deck with deckbrite and then brighten. Hopefully that will bring the color back close to matching. The new part did have a few pickets in the railing that had warped pretty bad that were just replaced last week as well as a 16 ft section of top rail. Hoping those will be fine to go ahead and stain with the rest as I want to get some protection on there since it already warped so quickly. What I need to know is if the 100 or 1500 would be better for my application. Will probably go with the redwood color either way. I realize the 1500 has a good bit more solids and lower VOC, but I don't understand if those would be good or bad things for my situation. Any help would be greatly appreciated.