When compared to the macbook air 13" for 2012. There is absolutely no reason to buy the 13" MBP over the MBA. Resolution is worse, HDD speed is worse, portability is worse, ram upgrades won't be utilized due to the max 1280x800 resolution.
Why would you upgrade a 13" MBP if you wouldn't see any of the benefits from the upgrade? The only thing worth upgrading would be the HDD to a SSD and by the time you factor in the cost of an SSD you would still have been better off buying the higher end 13" MBA.
Apparently you're smarter than Apple and those of us who value:
- user upgradeable RAM
- user upgradeable HD
- optical drive swappable for second drive
- Firewire port