Order a rifle that is already compliant.
1) Its quicker
2) Its much cheaper than replacing parts to make them compliant.
3) You may not even be allowed to order a non compliant rifle even if it was to be made compliant by your FFL...
(The dealer/FFL holder is the best source to know about that)
Buds will not sell (or at least will not ship if you purchase) a non-compliant rifle as policy and law.
If your local shop orders the rifle directly from RRA, they may send the rifle to the FFL, or they may not. It depends on if the FFL is allowed to receive non compliant rifles into stock. RRA may have a way to order the rifle you want in a compliant configuration already, they may not.... Ordering direct from the manufacturer can take weeks or more depending on their backlog.
Online retailers usually ship pretty fast. It depends on how long it takes for them to get the FFL information you wish to have the gun shipped to. If they have it on file, they usually ship within a couple days, if not, then the FFL will need to fax the info, and you are dependent on them getting it done, if they drag feet, then it slows down shipping.
The difference between the 14.5 and 16 inch barrels is negligible... The difference is that the permanently attached brake makes changing it harder if you was to want to do so.
I have owned a RRA Entry Tactical, it is a fine rifle.
The Windham is a good rifle as well, and it already comes compliant.
There is no need to fixate on the RRA, unless you just really want one.
Since you are limited by being in a ban state, all you gain is aesthetics... as all the features are disabled. You get the collapsible stock look, along with its weaknesses, but none of its benefits. You get the 16in barrel, but its advantages are offset somewhat by the lack of collapsible stock.
If you are concerned with best accuracy, then a longer barrel is for you... 18-20 inches. If you are concerned about longevity of the rifle (wear and tear) then a longer gas system than the carbine length is a good idea as well. (as I mentioned before, mid-length is better, less wear and felt recoil... rifle length is better still... my preferred is the Mid length)
Are you dead set on the carbine style? if not, an A2 or A4 rifle has less issues with compliance... sure its not a carbine, but they have their strong points as well.
If you want a carbine, go for it, its your choice. I suggest just getting the Windham, as its available and just as good as the RRA.