Go SOA and you won't regret it. It may cost a little more in the long run do to the amount of customization, but you'll also have the benifits of a smoother ride onroad as well as better flex off-road which is never a bad thing.
You'll need around 6"-8" of lift depending on the amount of flex. I'm SUA, run 8" and still rub fenders. If you go SOA with stock springs, thats around 6" right there, and all you need is a shackle lift or body lift.
If you SUA, you would almost have to have both which just adds up to more money.
anyway lol, do what you want to do, and do that the first time...I found that out the hard way. My SUA is great, flexes and rides awesome, but now I'm going to SOA in the near future and all the money I spent on the SUA is gone
Now if you do decide SUA's for you. I really like ProComp. For some reason a lot of people tend to trash ProComp, and most of them don't even have any experience with them. I've had mine about 2 years, with no sagging, great street manners, and about the best flex I've ever seen for an SUA.
Some other good brands that seem to be popular are the RE 4.5" kit and Rancho
Just my $.02