Where do you guys buy these items - big box or online?

Box store, walk in pick up items go install them all in the same day, not wait a week, hoping there the right item, there not damaged in shipment, no shipping charge.
When buying cans, outlets, switches I buy them in the contractors box, not one at a time.

Yup, me too. I can't remember the last time I bought less than six can lights at a time.

Big box stores will have just about everything most homeowners need for electric. Biggest exceptions would be odd switches (like 4-ways) or odd style cover plates.

There is an exception and that being specialized multi-functional plates and rare colored components. Occassionally you may need black, brown or grey switches and recpticles. I have noticed lately that the big box stores have scaled down carring these items in their inventory and they have to be ordered from an electrical contractor or online. I have even colored matched spraying plates to match when they were unavailable. Seems the white and beige are quite common though.

You guys are great, thanks for all the replies