I've recently purchased two rMBPs. (Jumping over from Windows, although, my first computer I used had Mac OS System 7

).
I bought a 2.4/8/256 rMBP on the
31/12/2013. It had the Part No. of
ME865X/A. I never opened it, because I wasn't sure if 256 would be enough for storage. So I hesitated for around 15 days. I returned it to a local retailer (where I bought it from), and upped for the 512GB version, which has the Part No. of
ME866X/A. I still haven't opened the 512GB either. It seems quite pricey for an extra 256GB (it's an extra AUD $350), so I'm thinking of just going with what I originally wanted, a 256GB model, maybe with a 16GB RAM custom build (w/ the extra $100 student gift card from Apple) - and going with a NAS/External drive RAID setup of some kind in the future.
Seems like Apple subtly moved to SanDisks for whatever reason (lower manufacturing costs? A heightened feud with Samsung? - I've read that
Apple wants to move away from Samsung manufacturing their hardware in future iPhone releases).
Not that there seems like there's any
significant difference between the SanDisk and Samsung sequential and random writes/reads for everyday usage, but just curious, are all 512GBs rocking Samsung SSDs? If so, what's their model number of the SSDs? Is there a way to tell if my initial 256GB model had a Samsung SSD (without opening the box)?
The reason why the 1TB PCI-e SSDs are faster than the 256 or 512GB PCI-e SSDs is because apparently there are four parallel lanes for the 1TB between the NAND Flash chips and the Controller on-board the PCI-e card
'The extra speed comes from having more flash chips on the card this a wider and faster path to flash memory from the controller. In the same way that a RAID array of rust based device is faster due to multiple channels used at the same time more flash devices means more parallel paths to flash.' Whereas the 512 and 256 have just 2 lanes for bandwidth - still super fast though.
I may just keep the 512. The extra RAM would probably cause me to have too many things open at once. At least with having a relatively large enough SSD, you won't have to worry about limiting what you store on your primary; for a long time to come.