Guess it's my turn to chime in.
The last time I rode 129 was about 3 years ago. It was in atrocious shape. You could ride it, but you'd be swearing. Frost heaves, potholes, broken pavement gravel patches. Truthfully, except for about 25km, its a boring road. Arrow straight and no services for most of it's length. It does have some nice scenic spots in that 25km stretch running directly beside the river.
Hwy 17 from SSM to Wawa is the Trans-Canada, as such, it's in good shape. Its *FAR* more scenic than 129 is. Theirs some great stops along the stretch that are right off the hwy. Iroquois Falls, where the marker for the Trans Canada was (It froze off in a cold snap!), Sand River Falls, Old Woman Bay.