if you can, wait 'til the ARM is confirmed in a rumored November 16th event.
Premiere, Photoshop, After Effects etc will always welcome plenty of RAM and HD space. In this recent discussion someone mentioned an upper-specs 16" MBP works great. I’d go with that or an iMac with good specs.
Edit: From personal experience: i5 13" MBP: not the best for heavy graphic work.