Lower receivers are controversial. Anyone who’s ever considered building an AR-15 has probably gone through the hassle of selecting a “lower”. This refers to the lower receiver of an AR-15 pattern firearm. There are a million to choose from, and they all market themselves as being different or ‘better’ than others. You can read a bit about them on Wikipedia.
Lower receivers are what house the rifle’s trigger assembly / firing mechanism. They’re the ATF serialized part of the gun, too, and so they need to be transferred via FFL (if you wan’t to be legal about it).
I’m not going to deep-dive lower receivers here. You’re probably here because you’re researching lowers, and so I’m not going to rehash “mil spec”, 7075 aluminum, cast receivers, forged receivers, billet receivers, hard coat anodizing, or the rest of it. You can find that stuff anywhere on the internet.
These are both 7075-T6 lowers, so the material is the same.
The Aero lower is more expensive, but you can see that the Aero has a little better machining — check the exterior and thread pattern in the buffer tube area — and features the ability to house a set screw to remove play between upper and lower receivers, which the Palmetto lacks.
I own both of these and I have no financial or business relationship with either of these companies. This is literally just a post designed to let you visually inspect two of the most popular lower receivers side by side.
I hope it helps in your decision making process.
I’ve had both of these lower receivers kicking around in my safe for a while now. This is why they each have a few small blemishes. They arrived from the manufacturer in good shape, so don’t think that these companies are sending out dinged up stuff.