I had a 15" MacBook Pro since 2007, but just replaced it with a brand new 13" Air. I also contemplated getting the 13" MacBook Pro instead of the Air, however I must say that I agree with Steve Jobs - the Air is the future of laptops. Yes, the Pro offers more expandability, you get the SuperDrive, you are able to expand RAM, Disk space, et.c. However, do I need the extra expandability? No. The MacBook Air is perfect for me, and comparing the base MBA to the base MBP, the MBA offers the best performance thanks to the SSD. Moreover, it's so sleek looking and easy to carry anywhere. The MBP of today looks not much different than my old MBP from 2007. The Air on the other hand - looks so modern and amazing.
For me, the MBA offers the best compromise between performance and portability. But then again, I have an iMac for my heavier tasks. Whether the Air is sufficient for you, I cannot answer. Do you normally upgrade your computers RAM/HDD? I don't. Instead I save the money, sell the computer and purchase a new one when it no longer suits my standards. Hence, the MBA is perfect for me. If you do upgrade your RAM/HDD, you should scratch the MBA. Then the MBP is definitely the best, and only choice for you.
If I wouldn't have had my iMac, I would probably have gotten a new 15" MBP, or the rumored 15" Air.
If you are an audiophile however, do note that the Air does not offer digital sound output through the headphone jack, unlike the MBP. If you often use a DAC for digital sound, the MBP would be a better choice.