You need to consider not just how much gear you'll be carrying, but how much weight as well. The 46 starts to get uncomfortable around 25lbs. I've had it up over 30lbs and spent a lot of time adjusting as I was hiking. The hip belt tends to slide down and put all the weight on your shoulders when it gets above 25lbs. If you can keep your weight under 25lbs and can fit all of your gear in it then I say go for the 46. Although trying to fit a week or more worth of gear is gonna be a challenge unless you are very minimal with your gear. It does hold a surprising amount though.
"As a well spent day brings happy sleep, a well spent life brings happy death." -Da Vinci