Of the two types, kennel matting is usually much cheaper. It can be bought in rolls by the foot, or in sections depending on the brand. It is usually treated so that it is antibacterial. Some types are made so that they are interlocking. They also provide a soft cushion surface for your dog that is shock absorbing and thus great for active dogs or puppies that do a lot of running around, jumping and playing.
Some are thicker than others, thus you will find that some types are better for more permanent locations while others are great if you travel with your dog and need flooring for a portable kennel or pen. On the downside, they make great chewy toys, especially if the interlocking tabs are not firmly pressed into place.
They are also usually non-porous which is great in that pet urine does not soak into the mats resulting in odors that you cannot get rid of. On the other hand, though, it means that puddles of 
water or urine will lay on the mats.
Kennel decking or platforms are used for more permanent kennel flooring. It is strong, durable and weather resistant. They are also designed to allow water or liquid to run off easily, so you do not have any puddles staying on the decking. One con to these is that they are usually fairly expensive, however once you have your kennel decking it is highly unlikely that you will need to replace it very often.
It is incredibly easy to clean, and is somewhat portable in that you can easily remove it from the kennel and run to hose it down if it gets very dirty.
