Sorry if it comes across as a stupid question, but with all these different types of hand guards available to throw onto AR's, ranging from everything from the classic two-piece plastic guards to the M1913 quad rails, Key-Mod, and M-LOK style, from non-free floated to free-floated, etc., is it really going to improve the performance of an AR significantly if I paid for a $200+ free-floated insert whatever mounting system handguard over the roughly $15-20 non-free floated plastic or Magpul handguards, or is it really just a personal preference deal?

Sorry, it's just I'm still not really making much sense of all the different hand guards getting thrown onto the market for AR's that they kind of make my head spin at how varied they are.

How much crap do you plan on hanging on the handguard?  

If the answer is a lot, then the next question is how accurate do you want the gun to be?

If you answered no to the first question, then a free floated rail won't do much to help you.
If you plan on throwing a light, a laser, a forward grip, an optic and a set of silverware on the handguard AND want to shoot dime size groups at 100 yards, then I would get a free float rail.

What he said, + I'll add some. IMHO, it depends on what you want to do with the rifle. If you want to squeeze out all it's potential accuracy (and yes, that means using a scope) than I'd say go for it. If you want a rifle that you can beat around, use irons or RDS on, I'd say rock the standards.
Some will tell you there's no downside to a FF (and that they're just as rugged) and I'll disagree with that. A FF rail places ALL of it's stresses (load/impact) directly onto the barrel nut. If you bang a FF tube hard on something, guess what... you've just placed immense stress on the barrel nut. Could that alter the "mating" of barrel to receiver? Stretch the threads? Alter the torque setting? I'd say YES, it could.
Standard type handguards will take an EMENSE beating will little affect to the barrel (at worst, they may pop off, and you put a new one on). They DO place a load on the forward part of the barrel, so yes, that will affect accuracy. But are you running a scope? How accurate do you think you'll wring out with irons? With RDS?
Again, it comes down to what you want to do with it. Personally, I don't like FF's, but I do run one on my scoped AR (and that get's babied). My "beater" (or more for hard use) use standard handguards.
YMMV.

I am biased toward free float hand guards. I want my rifle to be as accurate as possible regardless of the purpose for the rifle.

magpul handguards are a very nice upgrade to the standard issue handguards
and there are magpul rails that will mount up on them


true they are not free floated and high fashion, but the are very functional


if you find yourself wanting to shoot 200 yard or more targets,

you might find a freefloat forearm an advantage,

but plenty of people have hit at 200 yard ranges with iron sights and low tech forearms


the nice thing is you can easily run a couple of uppers set up for different scenarios


eventually you will have several AR riles and you will find a build that seems just right




i have a new build with a pencil FAXON mid length 16 and a 10.5 freefloated diamondhead forearm


it is a very nice shooting lightweight set up


my 10.5 inch pistol upper with the moe handguards out weighs it

You do NOT need to hang a bunch of crap on your rifle to benefit from a free float handguard.

Modular rails that are free floated usually have completely removable mini-rail sections.  My Danield Defense 12.0 MFR does.  I run the tube slick, no attachments of any kind on the sides.  Only a folding sight on front top with a QD sling mount right behind it.   There is a single 3" mini-rail on the bottom front for attachment of either a light or a bipod.

The point, however, is that the bottom mini-rail can be completely removed and the hand guard run completely slick.  Its real benefit is how it contributes to consistent accuracy.  Upward pressure on a non-float rail can affect point of impact.  If you ever shoot with a tight sling and a non-float type hand guard, you may see as much a a 6" change in point of impact with the sling tight, compared to running without a sling.  Where you place the handguard on a rest affects point of impact.

If you are just going to shoot bulk ammo at big targets, this does not matter.  But, if you and your rifle are capable of shooting small groups and want to do that, a free float rail helps a lot.  It does not have to be a quad rail with a bunch of unused rail slots.  It can even be a simple plain tube, freefloated, but with no rails at all, not even on the top..

Meh

Well, I guess with the build I'm going to eventually finish at some point (technically have the rifle itself done, just need to change out parts to my liking), I'm most likely going to be going with the Magpul hand guards then, both out of cost and out of expectations of what I want to wring out of my rifle.

My requirements for my rifle are making it sound like a jack-of-all-trades carbine that can take a beating and still work. For attaching things to the hand guard the most I can see myself throwing on it is a light and one of those VFG/bi-pod combo's (aka Grip-Pod/T-Pod). The rifles gonna be using a 1-4x24mm optic with a FSB and Troy rear BUIS and accuracy wise I'm aiming at being able to hit Minute of Man Sized Target at 300 yards (roughly 6-9 inch grouping from the prone position) with 55 grain or 62 grain ammunition, with occasional use with 69 grain ammunition out to 400 to 500 yards, coming out of a mid-length 16" CHF, chrome-lined 1:7 twist barrel.

Combined with the fact that the Magpul handguards feel comfortable due to the somewhat triangular shape of it, I think I kinda answered my own question after getting an explanation on what the pros and cons are.

Pics, please.