You are quite correct on the processor side ... If you compare like for like (ie the i5 based airs to i5 pros or i7 to i7) then the pros tend to have the faster processors. I suspect that is down to heat dissipation design restrictions, since Apples heat dissipation is primarily a passive design and hence dependent on the amount of chassis aluminium available of which there is a thicker amount on the pros.
Budget permitting i7 would be preferable to i5 processor, particularly if you have reasonably serious multitasking in mind. Might also want to consider upping the RAM to 8g.
From a gaming point of view, the other consideration is graphics .. I forgot to peek at that part of the specs, but I wouldn't be surprised if the pros have a better graphics chip with more memory. Admittedly I don't do much gaming though .....
In the end, you're an apple user, you've been using a MacBook since 2007, so you know how robust and well made they are. So you should really b looking at your new purchase as an investment with a 5 year lifespan .... If I were in your shoes I would buy the best I could afford...
But I digress you did express weight as a concern, so you do need to factor that into your decision making process and to what degree you want to trade weight for performance. I've seen people doing presentations with airs, comfortably holding then in one hand for the duration of their talk ... Couldn't really do that wth the pros.