As we say there is no free lunch. Free-float rails will obviously provide some measure of increased accuracy, although that is just a piece of the puzzle.
Some rails are better than others and all of them will have an advantage/ disadvantage. I really like the Centurion Arms rail for a variety of reasons. It's slimmer, it feels lighter and more user friendly when it comes to installation.
Rails like the Troy TRX are also a good option. Slimmer profile, rails where you need them, lower cost, etc... The real test is how will they hold up over time and after being abused. That is something that people need to take into account. DD rails are solid, and though they may be "bulky" in some minds they are also "grunt" proof which is a necessity.
In the end if you don't want rails and you only mount a light and sling and can get away with a particular set up then by all means do so.