It’s very likely that he could double his RAM and see little if any improvement in his video editing experience.
I find it hard to grasp how going from 8GB to 16GB would make a significant difference in performance if you’re editing, say, a 500MB file, especially if most of the time is spent doing disk I/O, which is often the case.
I would say that you should use at least the i7 with 16gb RAM.
My buddy does video editing with an i7 and 8gb and it's not enough.
Regards,
Jason