which mac to get air or pro

hello guys need a little guidence can any one help? I am looking to get a second hand mac can get a almost new one for £700 so I am debaiting which is best for me. I really like the air its so slim but also thinking about the 13 inch pro too . I all ready have a quad core imac but want some thing portable where I can copy all my cs6 and final cut pro across onto it. my debait is pro or air? it is really anoying that i may have to travel all the way to london to get an air which for me in leeds is like 200 mile drive.

Any way my question is this is an air with only 4gb able to handle final cut pro i could get a air 13 inch from london with 8gb but its not new new if you know what i mean..I could get an air with 4gb more or less new locally I have seen on gumtree a i7 with 8gb of ram but by same tokan seen a pro with retina advertised locally for same price i think its an i5 though. Any way what would you advise is a air able to handle final cut pro?

Just one small question about final cut pro x i noticed it running slow I have alot of imports in the window in final cut pro any way was running slow today booted up and it was running fine whats up with that does final cut pro require a reboot to clear memory from time to time?

Is their really that much difference in the weight in the pro and air tryed to pick one up at pc world but they glue them to the table stupid hay?

many thanks for advise my first time on the forum regards paul.