I place function above all else when buyng AR parts, with finish placing further down my list of important factors.
My current builds are on older Bushmasters, and Oly's. Very small problems with the Oly's, (more of an aggravation really) and no problems with the Bushmasters. But as I said, these are older lowers, so not sure how they stack up against new production, though I would suspect very little difference, if any.
I recently placed an order for several lowers because they were inexpensive. This brand has been selling well due to their cost I assume, and you see their name mentioned frequently on firearms boards. I got these just to "put away for a rainy day". Even though I don't put much emphasis on finish, I will say these lowers look and feel terrible. They look and feel like they are finished with 400 grit black wet or dry sandpapaer wrapped around them. The only reason this could be important is I can't help but wonder about their function, with the finish being this poor. And in my case this is something I may not know for months, or even years given my intended reason for purchasing.
Someone whom I greatly respect, and is a significant player in the firearms industry tells me that DPMS is a very good lower that doesn't get the respect they deserve. Unfortunately this conversation didn't come up till I had already received my 400 grit lowers. If I had it to do over again, I would spend the extra and get the DPMS.
Since this sounds like your first build, I think you would be happier in the long run if you spent the small amount of extra money, and got a lower made by one of the major players in the business.
As far as availability, if you order directly from the manufacturer, from what I read on the boards I expect you will be waiting for a few weeks. Dealers, on the other hand, may have what you want in stock, and probably at a lesser cost too. I order all my AR pieces and parts from dealers, because when I find an exceptional one, I enjoy building a relationship with them.
Good luck with your build, and please post pics.
As usual YMMV.