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This all sounds about right. It depends on the application, but the real benefit of a free-float is long range accuracy. That said there are some very cool looking free-float rails out there so its a matter of tastes... and budget. If you are going with a drop in rail I would recommend taking a look at Troy's rails. As long as you can get them they're great, I think they are somewhat busy with orders, but I've had good customer service experience with them, and they make great products.
+1 - No need for FF on a fighting rifle IMHO. Buy a Troy MRF-DI and never look back....