Re: free float tube
Knowing what your specific needs are will go a long way in getting you moving in the right direction.
For example, some people seem to think that having MAXIMUM real estate available for mounting everything from NV to Bipods to lights to IR illuminators to PDA's/ballistic computers to the kitchen sink is of high priority and they opt for options like the Daniel Defense, Larue, etc. which have full-length rails at 3, 6, 9 and 12 o'clock running the entirety of the handguard. Other people want lightweight, quick cooling, etc. and opt for carbon fiber, fiberglass, or lightweight aluminum, vented, etc. with no rails or fewer, smaller rail sections that can be added/removed/positioned as necessary.
I have everything from monolithic uppers to the basic, factory OEM float tubes/handguards and everything in between and each serve their roles as necessary. It really all comes down to what you want/need from your particular setup that dictates what the best options are for you.
Also, just as a cautionary word of advice..."AR-10" does NOT equal LR-308 for the purposes of shopping for handguards/freefloat tubes. They each require options specific to the platform and with the LR-308, DPMS changed receiver heights a while back so you have a further complication of determining which version you have any buying a handguard to match. (Not a big deal on the DPMS in terms of the height difference unless you are going to be mounting sights/optics across the receiver/handguard, etc., etc.).