[Lammy]

I see them as fundamentally different because PDAs mostly didn't have network connectivity at all, while modern phones are connectivity-first and gained functionality from there. It was novel to have a PDA with a modem that did anything, much less provide connectivity back to one's home computer.

[jacobgkau]

That's a fundamental difference in their history, but not in what they turned into. Especially, again, in the context of screen sharing-- a PDA would've needed to have networking in order to run GoToMyPC. It's "device in your pocket that lets you control a bigger computer with remote desktop" either way.