I have both a Burberry outlet store and a "normal" Burberry boutique near where I live, so I visit both very frequently.
What I have found is that the outlet store does carry styles from past seasons that were previously at the normal Burberry boutique, often without any flaws.
During sale season, I have found numerous times the exact same style bags at the outlet store (50% off) that were on sale simultaneously at the the normal boutique (50% off) on the other side of town HOWEVER, the outlet bags all has some form of scratching/damage to the leather. Not one was in perfect condition at the outlet store. When I pointed this out to my SA, she was really embarrassed and confessed that the damaged items were selected to be sold at the outlet location at the exact same discount price!! In another occasion (during the summer sales at the normal store), I have noticed that the exact same style bags were being sold at the normal boutique (50% off) and at the outlet store (60% off), although the outlet store bags did have minor flaws (mostly scratches on the leather).
Sometimes, the outlet store does get merchandise which I had never seen at the normal boutique. I suspect that some of this merchandise is created specifically to be sold at the outlet store and has a little less quality than the regular merchandise at the normal boutique.
A good way to tell the diference between last season's normal boutique merchandise and merchandise created specifically for the outlet store is that past season's merchandise is very limited - they only have certain sizes. When I see piles of shorts or white polo shirts with every single size available and even multiple copies of each size, I always suspect that it was made for the outlet. Lastly, use your judgement! If the regular Burberry high quality of materials, cut and stitching isn't there, just don't buy it. If it is, then you've scored a bargain and it doesn't really matter which store it came from.