I was in a similar situation about 10 months ago. I originally bought a 13" Air. I loved it but became disenchanted with the viewing angles and low color gamut of its screen. Also, because I usually have a ton of tabs open in Chrome, have some very large spreadsheets open in Excel, and use Handbrake occasionally, I started realizing that only having 4gb of non-expandable RAM might be a problem for me -- especially since I might want to run Windows 7 in a VM on my machine in the future.
I decided that I needed the expandability of a Pro more than the mobility of the Air. And I didn't want to compromise on the screen qulaity either. I initially chose the 15 inch Pro with anti-glare, high-res screen. It was a great machine. I was so enamored by the screen size that I decided if I was going to go big I should go all the way. So, in the end, I ended up with a 17" Pro with anti-glare screen (I actually bought a glossy first but couldn't stand the reflections). I upgraded to 8gb RAM (I may even be going up to 16gb soon) and an Intel SSD. I also put the original 750gb HDD in the optibay and bought an external blue-ray drive to satisfy my occasional need for it (OS X won't play blue-rays directly, but you can rip them and play them with 3rd party software).
I am extremely satisfied with my decision to go with the 17 Pro vs the 13 Air. Since I usually just travel with my iPad and only carry my laptop from room to room around my house, the decision made sense. You'll have to figure out what aspects of each laptop you value more. They are all great machines.
As others have already said, I would wait a couple days to see what Apple announces at WWDC before making your decision.
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I take it you haven't used one?
For CPU intensive tasks (like Handbrake), the Air is definitely way slower. For non-intensive tasks, the speed difference is much less noticeable (as long as the Pro also has an SSD).