I originally ordered the riMac with 256gb ssd but returned it because of other issues. Now I'm looking to reorder however im stuck between choosing the 256 or 512gb ssd. I've read that the 512gb ssd is a quicker and newer version from Samsung. Is this 100% correct and what difference would I notice by going with the larger flash drive? Would the iMac start up slightly quicker? Thanks
The 256GB is a lottery between Samsung and SanDisk (SM0256F and SD0256F respectively). The 512GB and 1TB are Samsung only (SM0512F and SM1024F respectively).
Differences between the SM0256F and SM0512F are very minimal. Between the SD0256F and SM0512F, differences are quite large in write speeds (by about 150-200 MB/s, because the SD0256F is a slower SSD).
SD0256F writes: 550 MB/s.
SM0256F writes: 670 MB/s.
SM0512F writes: 720 MB/s.
It won't start up any quicker, but if you do write-intensive tasks, the 512GB variant may speed it up a bit quicker.
That said, you should go for the 512GB variant so that you don't have to constantly monitor how much free space you've left.