I do believe they are all excellent choices, there isn't a bad choice in those options. I think you will be pleased with any of them. So go with the one you like or is at the price point you prefer. I pray for problems like these where my choices are between such good options.
I have a WOA 18" SPR barrel that I am increadibly pleased with. ADCO bead blasted it and I really wished I spent the cheese to have it flutted at the time. While flutting isn't the a real big feature, it is a nice detail that I like. It is my favorite upper, so I don't really want to mess with it now. I would be bummed if any accuracy was lost on it. The barrel has been very accurate for me and completely reliable. It even handles Wolf ammo pretty decently. It has really made me a fan of the 18" barrels.
The Sabre is hard to beat for the features. It is flutted and bead blasted. The WOA came with a brushed stainless feature and I paid a little extra to have it bead blasted. I haven't heard many complaints about Sabre. If I were going to do another SPR style build, I would probably go for one of the Sabre. Again, flutting is a huge deal, but a nice detail that I think always looks good.
Here is my 18" WOA build: