The verdict
For a small B2B team whose website exists to generate leads, I would pick Webflow. Every B2B site I manage runs on it, and I would choose it again for a modern marketing site. For a team whose revenue comes through a catalogue and orders, pick BigCommerce.
Do not make Webflow carry a large shop, and do not make BigCommerce carry a content marketing plan. If selling products is the core of the business, test the catalogue and checkout limits on Webflow before you commit. If you need both a strong site and a serious store, plan for two systems with clear owners, and check how they connect first.