Need new daypack -- 30 or 40 liter?

I need a new daypack and was considering either a 30 or 40 liter. Has anyone tried the REI Trail 30 or 40 packs?

http://www.rei.com/product/880838/rei-trail-30-pack

http://www.rei.com/product/880839/rei-trail-40-pack-mens

It's it makes much difference I am 6'2" and of wide beam build. My hikes tend to be a bit shorter but more strenuous. Thanks for any help...

Would it be a problem to get a bag that was a little too big? The price difference between the two bags is $9.50