Kangaroo: This one is another amazing product from Ohman. Now that we have the limitation of amps in the old Billet Box you can really go hog wild with the different coil heads you can use. Personally I have been using both the .5 ohm SSOCC coil heads, and the .5 ohm Clapton coil heads.
With the roo there is no worries of having the airflow restricted on the lower ohm coil heads, and included with it is an o ring which you can use to restrict it. Personally I've never had to use it, but I could see it being useful for someone who is more in the really restricted lung hit / mouth to lung hit.
The flavor is what you would expect from the subtank coils. It's very very good, but to me not quite on par with the Uno. Again this is just my opinion and you mileage may vary.
One con that I have heard from other people (personally I haven't had any issues with this but it could be a problem) is you have to lower the glass to the point where it's almost off to get the coil head in. If you're not careful you could end up damaging the glass if it falls out.
BB Sport: The only difference between the sport and the roo is that out of the box the sport has really restricted airflow. It's not something you can change. Depending on the coil head you get you could cut off the airflow completely.
For some users this may be a good things, but I have a couple of cons for it. If you're like me and like to be in the sub-ohm range it could lead to an extremely hot vape, or even end up burning. The other con is that unless you like a very restricted lung hit or mouth to lung hit it probably won't be an appealing vape for you.