Again, if the plain existed, then it is likely that both routes were followed. However, I maintain the inland route to be the easiest because traveling alongside a mighty river such as the MacKenzie River, is much easier than crossing the many mighty rivers that flow into the Pacific. This is especially true for people traveling on foot.

The Cordilleran route is not only easier, but also more open to the rest of the continent. You don't have to find paths Eastwards through glacier filled mountains to reach the rest of the continent. Even the paths that did lead through the mountains would have been avoided by the megafauna due to the lack of food on the glaciers. I say the easiest route would have been more popular for both the megafauna and man, making the Cordilleran route the one by which the American continents were populated.