I haven't used the exact models you are asking about. I had an Oceanic Air XS. Personally,... I hated it. Not the idea of it, just the design of the Air XS. It was not built in mind for someone with small hands & short fingers. I went back to a bungee'd Octo. The way the air 2 is designed is much better (I service them). I have no experience with Mares prducts. Anyway, The general Pros & Cons of an integrated air source:
Pros: Elimination of 1 hose for better stream lining & less clutter, The air scource is always handy in the same place (no more trying to find the octo when it falls out of its holder. That said, I have never had an octo fall out of a bungee necklace).
Cons: If you do not already,... you will need to get used to the donation of the primary regulator (the one in your mouth)as the integrated air source is too short to donate, on ascents to vent the expanding air from the BC, you will have to either use an alternate shoulder dump, pull the inflator hose (has a cord that is attached to the shoulder dump valve) or take the regulator out of your mouth to dump the air, the power inflate & deflate buttons are in a little different spot you need to get used to that. Also they don't tend to breathe the greatest, but then most octo don't either. It is an emergency device, designed to safely get you to the surface.
Most of the "Cons" really aren't Cons, it is more just needing to get used to a different configuration.