The durometer of Bio Pro XT is 75. The durometer of Bio Fin Pro is 65. So, in other words, Bio Pro XT is stiffer. As for average durometer of paddles, I wouldnt know. Youd have to look around for that. But off the bat, Id guess theyre higher.
Lower air consumption is dependent on many variables, from how slowly you breathe, your experience level, how much effort you're exerting and so on.
For me, having paddles meant way more effort. Having my original Apollo pro fins meant way less effort. When you're exerting less effort, then yes, your breathing can be calmer.
You have to try them out for yourself to see how well they work for you. The stiffer the fins are, the more "effort" it'll take you to fin. It's dependent on how much you can tolerate kicking. Meaning in other words, do you cramp up easily? If you do, then stiffer fins mean that until you get really used to them if at all, it'll equal more effort for you. And that translates to breathing harder.
Try between both those two fins you mentioned and see if there is a significant difference in more effort for you to kick. I wouldn't know since I've only tried the original ones. If you like the stiffer one more and feel that yes, it does take more effort, you can stick with it till your body gets used to it. A lot of people here take their stuff to the pool and practice with it till there is no more cramping up and so on. Or you can go with the one that's less stiffer. Either way is fine. It's all up to your comfort level.
Do understand that having Apollo fins doesn't magically lower your air consumption, but if it's less effort for you kick, it's part of the overall picture that you're on the road to towards lower air consumption.
Anyway, congratulations for getting those fins! Hope youll enjoy them. I seriously adore my original Apollo fins!
Hope that helps.
BTW, if any of my information is wrong, do feel free to correct me.