I just rode the second route you listed a couple of weeks ago while my neighbors (two adults with four children aged 5-10 on two triples) rode the WVSB route. When we compared notes, they felt they had more traffic on the portion near Salem than I had skirting that mess to the east. However, make sure you have your hammer ready for the stretch between Stayton and Jefferson and do choose the time you arrive in that region with care. There is no shoulder, but most of the day the traffic is so light that it is a non-issue. Still, the faster you are moving along there the better. Thankfully, the bridge between Marion and Jefferson was rebuilt a few years back. That used to be a narrow, double-blind bridge; now it is a nice, wide surface.
There is a similar issue along Peoria Rd/Coburg Rd. Peoria has a nice shoulder and great surface while Coburg Rd. has new chipseal and a slightly too narrow shoulder. Both are fine, even great, except when the Eugene to Corvallis commuters are racing to work or home. For some reason, the Corvallis to Eugene commuters are much more considerate.