Which SSD is Apple using?

They are Samsung or Toshiba drives.

 

Yours is made by Toshiba.

 

Toshiba.

Strengths:
1. Faster than SATA HDDs.
2. Wear leveling.

Weaknesses:
1. No allocated space for real-time data redundancy and ECC error correction. This is called "over-provisioning." (This is obvious from the 512G capacity. If it had over-provisioning, it would be rated at 480G or 400G capacity.)
2. Sub par transfer speeds compared to the SandForce based SSDs from OCZ, Corsair, and OWC as shown when the Apple (Toshiba) 256G is compared to the OWC 200G:
http://barefeats.com/imac10d.html

 

Exactly "512" Isn't really a definitive sign. a 25% over-provision ratio would be even on a power-of-2 number. (e.g., 512GB "usage" with a 128GB buffer for 640GB total would give you exactly the numbers. ). It is also very difficult to have very effective wear leveling mechanism without any buffer. ( only is cheesy disk completely empty context would it be effective without one for decent amounts of static data. )

They may not be doing any fancy EEC (to use cells after would normally consider them worn out) and duplication ( so can do RAID like cell access) but those aren't the only usages for an over-provision buffer.

It appears that Toshibas SSD may be a tad "old". The Toshiba site says that the newer HG3 series SSDs do support TRIM. The system profiler snipper above says no. Suggestive that this is one of the older models. That may be why the price is better than other quotes on the web.