I use my full suspension on trails where there are longer technical sections, such as rock gardens, large log piles (not just a log) and downhill sections that can be sketchy. The suspension doesn't make me lazy, its doing what it is designed to do, taking bigger hits and drops, and my full suspension frame is also built for this type of riding, its just a beefier and much heavier build. When I'm riding swoopy single track that winds through trees, or more of a cross-country type feel where speed and agility mean everything, I bring out my hardtail. There is nothing like the snappy speed of a hardtail on hardpack singletrack. Each bike is so different from the other, I so enjoy the change-up.

If you have back problems and your trails are quite jarring and full of technical features, you'll be able to ride longer with less fatique and more confidence on a full suspension bike. Its just tuning your bike to fit your weight that can be a little more complicated and then a slight learning curve on climbing with rear suspension. I started mountainbiking on a hardtail, then bought a full suspension bike to ride places like Moab, Fruita and Sedona out West. Here in Minnesota, I use my hardtail 50 percent of the time though.