700 g difference. It's pretty close. My guess is you might have a hard time telling which is more heavy if you blind your eyes and weigh one in each hand.
Unless you have a handicap you would be able to tell instantly. It's a huge weight difference--the MBP Retina is 50% heavier than the heaviest MBA. That's the additional weight of an iPad sitting on the MBA.
The weight difference between the iPad 2 and the new iPad is quite noticeable and it's just 51 grams. The difference between these laptops is 14 times that.
700 g difference. It's pretty close. My guess is you might have a hard time telling which is more heavy if you blind your eyes and weigh one in each hand.