As Meirril pointed out
here, it's likely that the price of strong boxes/ease of gathering material will still give them a slight advantage, as pelts are generally a bit harder to find and more in demand than wood. Also, given that nobody except a couple of mage classes has any use for weight reduction now, I don't think that really gives backpacks any advantage (and strong boxes are still totally fine for a bank anyway).
I'm expecting people will just buy whichever one happens to be cheapest or more available, and probably only those couple of mages who tend to be low on strength will have a strong preference either way. However, I'll definitely be listening to the feedback from test server and if it seems to be called for, some tweaks to the weight or weight reduction of strong boxes isn't out of the question if there seems to be a need for it.
LINK
(DominoDev) Re:Backpacks on Test: Now Bigger. And Strongboxes the same size (But not same weight)
