I have a few of both, but in the summer I prefer the external if I’m carrying over 30 pounds. I picked up an ultralight internal pack for much lighter loads.
I did a test last year when I started section hiking the AT and wanted to take the most comfortable pack. I took 40 pounds of gear and 3 packs to Acadia for a weekend (I have 13 packs, but narrowed the list down to those 3). I was also trying out different tents and gear, but that was on a different day. I loaded an internal up and went on a 4 mile hike, coming back to my car, where I took all the stuff out and put it in the other internal. Then I did the same loop trail and came back to the car, loaded the external and headed back out again. I was amazed at the external pack as it carried the weight so much easier than either of the internals. Even my older brother was amazed at the difference, he said if he hadn’t watched me move the gear he’d have sworn I left some out. Two more bonuses are that it’s much cooler on your back in the summer and you can dry clothing from it easily.
I ripped mine bad falling down Bemis Mountain, and while the repair may hold, I picked up a REI Wonderland for $20 at IME for this summer. The externals are a tad heavier, but carry so much better I doubt you’ll notice. If you were closer I’d loan you a few to try.