I know your order has already been placed but I'd like to toss my 2 cents in.
Warmoth makes great stuff regardless of the price. In my opinion, unless there is something you're specifically needing, get your neck from the Showcase. The reason I say this is because you can actually see what you're buying. Now, back to Warmoth quality, in my opinion, you can trust what you're going to get from them, and if the specs you're looking for are in the Showcase, then it falls down to looks. I like maple fingerboards so I'll use that as an example, do you prefer a reserved look with not so much figuring in the wood or do you want enough birdseyes on it that it looks like someone covered it with a bowl of oatmeal? If it's a highly figured look your after then the Showcase is the way to go. The reason I say this is because you can order a AAA grade neck but it may not look like what you had in your imagination. Case in point, on a body, our friend that got the black washed LP body recently. I totally feel for him and can appreciate his feelings when he first opened the box. He had an image in his head and that body didn't match that image. It doesn't matter that that body looks like a million bucks, which it does, it's just not the image he had in his mind and was waiting for. When you order something without being able to see it, well, that's a risk you have to be willing to take. Now, again, that has nothing to do with quality, it's all personal preference on how something looks compared to what you were expecting it to look like.
As for the prices of the necks, I'd say with Warmoth, as far as quality goes, you're going to get similar quality from a 150 dollar neck that you would in a 970 dollar neck (everyone remembers that one). The build quality is going to be there regardless of the price. The next thing it falls down to is going to be the type of woods, the grade of the wood, the figuring.... Now, I said the "grade" of the wood but I'm pretty sure that Warmoth doesn't skimp. For myself, when I go looking for a neck in the Warmoth Showcase, I set the parameters of the specs I'm looking for and then it all falls down to what it looks like. I like highly figured necks that has the figuring well balanced across the entire neck and the head. I wouldn't want something that has a clump of birdseyes at one end and then scattered here and there over the rest.
One last thing, I'm not an expert on wood so take this for what it's worth, which is something someone told me once a long time ago.....and hopefully someone here can confirm or deny this, but I heard that with flame maple necks, looking at the back, tighter flames have less tendency to warp than ones where the flames are further apart from each other.
Oh, one extra last thing, and I do know this for fact because I was a professional pool player for most of my adult life, birdseye maple can snap like a twig if there is a fault inside the wood. I don't know what the experts would call it but in the pool world we call it a "birdseye break". I've seen it dozens of times over the years. Someone has a 5,000 dollar cue, birdseye maple, and they accidentally drop their cue and it snaps right in half. Granted, you're not going to be throwing your guitar around, and pool players don't throw cues around, but accidents can happen. If you go with birdseye be very careful with it because you just never know.
MULLY
Yes, my pool cue costs more than both of my Warmoth's put together