external SD is slower than internal.That used be the dealbreaker for me, however I very rarely pull the sd card out. Although I would be curious at the speed difference between using the S6 internal storage vs an S5 and the fastest card available.
I played with the s6 and edge today and its literally like every other android, I use a 6+ now so it felt super tiny, I might still get the gold one, but a Note with that build would be dope, I can't say this feels premium to me as i've used iPhones prior,but this def feels better than any prior samsung. I honestly feel we are at a point where all devices are the same, so you just cop what you can afford, build quality you prefer, and best cam.