From Apple discussion groups:
Only with the packaging and connections. A 'standard' SSD is in a form factor of a 2.5" x 7-9.5mm 'box' with a SATA connection whilst Apple's latest flash storage devices are more like daughter cards that are connected through the PCIe bus (making the flash storage in the newer Retina models a bit faster than the old SATA connector).
External flash drives use USB, which, I believe is much slower.
> On Jan 13, 2016, at 10:07 AM, CJB <[log in to unmask]> wrote:
> Thank you - but aren't flash drives the same as SD cards?
> But a 1TB conventional drive seems OK.
> On 13/01/2016, Stewart Gooderman <[log in to unmask]> wrote:
>> MacBook Pro 13” can be gotten with a 1 TB hard drive.
>> MacBook Pro 15” can be gotten with a 1TB flash drive.
>>> On Jan 13, 2016, at 9:14 AM, CJB <[log in to unmask]> wrote:
>>> BTW if anyone knows of a brand (not Lenova with in built spyware) that
>>> offers laptops with proper hard-drives do let me know. As others have
>>> opined re: SD cards aka solid state 'drives' of limited robistness,
>>> please let me know.