The Glare would have been more helpful in earlier versions when mobs could spawn at light levels below 7. It's pretty challenging to see the difference between level 7 and level 6, for instance. Now that 1.18 changed that to level 0, it's incredibly easy to see even without the F3 screen. Just check for the darkest spots. It also doesn't make sense conceptually, as the entire concept is that it actively seeks out the darkness but gets grumpy upon finding it.
Allay actually seems really good. The ability to use it as a long-range sorting hopper is excellent, and it costs a fraction of the price of an equivalent hopper system. The design being almost entirely based on the vex is strange, but aesthetics were never essential to me. The affinity toward music seems pretty random but would be an excellent way to control their movements. I assume it will have a mechanism to control when it drops the items without the presence of a player, which would make it very practical for compacted sorting systems.
Copper golem gives a use for copper, which is great, but the benefit is a little disappointing. It's primarily valuable to redstoners (as opposed to Allay, which is beneficial to explorers and redstoners alike), and even then, there are alternatives. I will say that the other options also have flaws. We don't have very many game mechanics that are designed to be random, but the ones we do have can get expensive and aren't really made to interface with redstone components. This mob will be explicitly made for randomizing redstone (likely more unpredictable than a chicken) and would make randomized more compact. However, the fact that it oxidizes after a while makes this mob impractical for automated machines (you'd have to manually replace it after a period) unless it implements some version of the waxing mechanic. However, the "oxidizing" feature is liked by builders or other creative types, so this mob has a solid following.
As of right now, my vote will definitely go to the Allay since I think it contributes more to both the redstone and explorer communities.