I have a 1.2/512SSD Macbook 2015. The Retina screen is/feels sharper then my MBP15 Retina.
The speed of the diff processors has been benchmarked, the 1.2 is impressive jump, and the 1.3 is nice if you have teh $ and are CPU bound with heavy apps that may show marginal improvment - per benchmarks. The 1.2 is what I decided on, and have been very very pleased.
Overall, loving the Macbook 2015. I use my MBP for very heavy lifting, i.e. video encoding and work related heavy apps. But Macbook 2015 has been able to run almost everything I have thrown at it, with surprising efficiency and speed.
I just picked up the 1.2 MacBook yesterday (space gray); it's a more portable companion to my i7 15" MBP.. I got the CPU upgraded mainly for the double storage, 512 vs 256 GB.. I would have had to wait if I wanted the 1.3 CPU, those are considered custom builds and non-stock items. If it were to be my only MacBook, I would have thought about it more, but for reading news sites online, e-mail, iBooks, and other standard apps this new MacBook can handle non - cpu intensive chores quite handily.
I have to say, I LOVE this Mac!!!!