The STA adds some weight, but I have found that I prefer to run the cam bands directly through my backplate. I like how the tank sits closer to my body and the tank, particularly a steel tank, feels more stable. If traveling weight is a concern, not having an STA reduces that weight in your luggage. If you go without an STA, you'll remove the cam bands when you pack. Just practice threading the cam bands a couple of times, especially the part about running them through the buckles properly. Pretty easy once you get it, but it's not super intuitive at first.
Edit: There's lots of great input on here and you may feel as if now you have too much info and seriously don't know what to do. The great thing about a BP&W set up is that it's modular. You can make adjustments, additions, and subtractions quite easily even between dives.