Deck stain choice and prep question

Hello,

I am a new member and am really delighted to see a website dedicated to giving unbiased reviews and advice for staining decks.  I live in a 3 level townhome in Virginia, with the deck and deck stairs attached to the second floor; all areas of the deck to include the underneath are stained. 

I used Olympic semi-transparent acrylic water based redwood stain and sealant the first time around about 2 years ago.  It is time to redo my deck.  My questions are simple:  do I go with another water based stain that you recommend, or should I used a oil based stain this time around?  Finally, what type of deck preparations should I utilize based on either a water or oil application, and what brand would you recommend? 

I do want to use a semi-transparent stain and sealant again.  Thank you for your help!

Clay