OK, I am not an expert on such matters, but from what little I do know, you are talking about aftermarket batteries - decoded means that they will work as proper Canon batteries - ie show the remaining charge and can be recharged on a proper canon charger etc. A coded one will do the job of powering the camera, but nothing (or little) else, so may be even cheaper, though a separate charger may be needed.
I have been looking at some to go in a cheapo battery grip for my 5d2 - £40 for the grip, and a further £20 for 2 batteries is way easier to find than £150 or so for a proper Canon grip, plus a further £100 or so for 2 genuine Canon batteries !
Having never used a grip of any sort, it makes sense to me to try a cost-friendly version first, and hey, if it works fine then until I try a proper canon one I will not know the difference, but will have saved around a hundred pounds !
There are stories of aftermarket batteries not fitting, blowing up, causing death to all within 1,000 miles and so on, so I have been asking for help from those who know more than me when choosing what batteries to buy, but on my old 5d, the cheapo batteries I bought all worked just fine.