I have done a test comparison of the standard Canon LPE8 battery (NEW) and this Maxsima brand (also NEW) by running a Live View feed continuously on my Canon 650D. My Canon battery lasted half an hour longer.
The reviews I see on here claim the opposite and I would not doubt them. But I suspect most are comparing to an old and used Canon battery. Also, if comparing by just taking still frames without using the LCD display, both batteries will last long enough so the perception that Maxsima is longer may be greater. Just giving possibilities as to why other reviewers may perceive the Maxsima to have longer lasting charge. Of course, I may have received a poorer quality one but then if that is the case you would have to beware of purchasing this item on luck of receiving a good one. I dont think that possibility is the case, though, as this battery performs well and cleanly. It also does a full charge quickly.
However, for this price (around a tenner), its a very affordable and recommended purchase for using this battery as a secondary back up...but not as your primary battery. Well, no harm using as your primary but your Canon battery has the longer charge despite the higher mAh on the Maxisma so it makes sense to keep using your Canon as primary unless it has degraded in performance over time.
My rating reflects value for money, if the price is considerably more than a tenner then I would reduce the rating to a three or two star.