this may have been beaten into the ground and asked many times before but im not computer savy and dont know how to do a site search so here goes....

are rra and olympic arms good manufacturers and of the two which do you prefer and why? ( just a fyi i am looking for a m4 flat top configuration and plan on mounting a eotech with some sort of folding buis either an a.r.m.s. or a mi inc)

thanks for any help you guys can give me

RRA, of the two.

And why? Why not.

My preference is RRA. I have owned both, and quality of the Oly was good. Mine had a bad trigger, that would cause unintentional double taps, but I think the previous owner had tried to "lighten it up" a little too much. But fit between upper and lower was sloppy, and reliability while good was not great.  I also have owned a DPMS, and it was the most unreliable that I have ever owned. RRA has been perfectly reliable since day one, fit and finish is excellent. IMO, top manufacturers of AR's goes like this.
1. Colt
2. Bushmaster, very close second
3. RRA & Armalite, very close to BM

RRA.

Good quality stuff.

Good customer service (except for some people that called during the Wrong Time Of The Month)

They're my company of choice.

WIZZO

I have an M4 oly upper and a RRA lower, it's the tightest AR I own even pins are tight.

I have been extremely happy with my olympic.  I have the rifle and 2 seperate uppers.  Both uppers have been pretty much flawless.  Accuracy has been very good, 100% reliable with every type of ammo I have shot through it (even Wolf, Natec polymer, and the horrid Greek olympic), good fit and finish, and reasonably priced.  Olympic also has a lifetime warranty.  I would buy from them again without hesitation, and I am planning one buying a seperate lower from them to take my spare upper and make it a complete rifle.  
                                         -K

ETA:  Welcome to the board!