I like 'em for some people. I work in the outdoor industry and see both sides and uses.
Trail runners are attractive because of the weight savings, easier initial cost, cooler temp (for hot days), and what most people would consider a grippier sole. Boots are more supportive, longer lasting, and keep debris out better. Both work well.
If you're a heavier person, you may need a bit more support. A hybrid boot like the Salomon Quest 4d is an excellent choice for a lot of backpackers, hikers, and scramblers. The grip is also really good and it's relatively roomy to accomodate foot swelling and insoles. One thing I love about this boot is you can lace it lower like a trail runner but lace it higher in adverse conditions, descents, and injury situations. I've got a pair of these and love them - but they do run a bit hot.
If you have specific questions I'd be happy to help more.
