Few questions: 1. Late 2013 15' rMBP (base model) vs same but 2015= worth upgrading? Besides force touch, are the speed updates really that much worth it? 2. Late 2013 15' rMBP vs. 2015 13' rMBP: Which one is faster? I think the only difference in the 15 inch was that it has Iris Pro. But would the Late 2013 15' rMBP Iris Pro be slower than the 2015 (non-pro) Iris in the 2015 13' rMBP? ***I don't do photo/video editing or anything of the sort but I do use it in clamshell mode with dual-screens; however, I want enough power to once in a while play the latest games while keeping the most portable machine possible. I'm wondering if I can get away with an Air or not. Thanks!