Is it healthier to take bulk former like Metamucil or eat lots of greens?

That's an easy one! There is no substitute for fresh fruits & vegetables. No commercial fiber product can replicate the antioxidant, mineral, & vitamin benefits of produce. On the other hand, some people tolerate raw vegetables poorly with bloating, gasiness. For these people, or when vegetables may not be readily available, fiber supplements may suffice for bulk. Distinguish water soluble versus insoluble products.