I have a four year old iMac that I'm looking to replace. I'm a teacher so I get education pricing. I'm having trouble figuring out the better buy based on performance. Is there a significant difference between a $999 MBP 13" and a $1049 MBA 13"? My main concern is the spinning drive in the MBP so the only upgrade I'd be willing to consider is for a solid state drive, even though I'd lose a lot of capacity. I don't need to do a lot of heavy lifting but I'd like the machine to last at least four years. The MBA's are brand new so how do I decide? Any suggestions?