Let me echo what others are saying about portability vs. power.
Unfortunately you and those others have no idea what they are talking about. The difference in weight between the two (we are talking 13" models here, not 11" Air vs 13" MBP Retina!) is not that much. If you hold both machines you won't notice the difference at all.
As for battery life: yes it is nice the battery indicator in OS X tells you the machine will run for 15 hours but unfortunately it is a complete guess based on how you used the machines in the last 5 minutes or so. In reality it'll be less than that. When you do specific tasks on both machines you'll see that battery life isn't all that different. That 15 hours is nice when doing almost nothing with the machine but when you actually do work it suddenly becomes 3 hours or even less because it completely depends on what you are doing with the machine. The amount of time that calculator tells you is nothing but an indication of how long the battery might last, it is not an exact measurement whatsoever.
The difference in hardware between the 13" MBA and 13" MBP Retina is very very small. Yes the Retina one is a bit heavier but it is also smaller in size, comes with 2 Thunderbolt 2 ports (instead of 1 Thunderbolt 1 port), HDMI and a proper display (it uses an IPS panel instead of TN that is used in the Air; that means proper colours). Thunderbolt 2 ports also allow you to use DisplayPort 1.2 instead of 1.1a. Having two Thunderbolt ports is also a big help because you can hookup a display (vga, dvi, hdmi, displayport) and the gigabit ethernet card. That setup is cheaper than a Thunderbolt dock.
Another thing I noticed: the Retina one has a more solid build due to not having a tapered design. The Air feels a bit flimsy on the front and it also makes it more difficult to grab (some have dropped their Airs due to it slipping out of their hands). You'll have a better grip on the Retina one.
The only real problem is the difference in price. I'd go for the Retina one because of the IPS panel alone. It just make such a big difference to your eyes. I find it more comfortable to look at. The Retina part is just a bit of a gimmick. If you turn down the resolution you'll get the same size fonts as with the 13" Air but a bigger working area.