As an Amazon Associate I earn from qualifying purchases @AMAZON
2019 iMac 5K: SSD Speed vs Transfer Size
Related: 2017 iMac 5K, 2019 iMac 5K, 4K and 5K display, iMac, iMac 5K, Macs, memory, SSD, video
MPG tested the 2019 iMac 5K 3.6 GHz Intel Core i9 8-core / 128GB / 2TB / Radeon Vega 48. Purchase with 8GB memory, then add 64GB or 128GB OWC memory. See recommended Macs for photographers and videographers.
These tests made possible by loaner gear from B&H Photo and OWC, so please buy your gear at B&H Photo and OWC/MacSales.com using any link from this site or MacPerformanceGuide.com, ditto for OWC/MacSales.com. See also 2019 iMac 5K: Recommended Models and Accessories.
Unsure which Mac to get or how to configure it? Consult with Lloyd.
Sustained transfer speed vs transfer size
Real world speeds through the file system using diglloydTools DiskTester.
disktester run-sequential-suite --test-size 8G
The 2019 iMac 5K flash drive (SSD) offers very similar performance to that of the 2017 iMac 5K, but it reads faster and writes slower! It’s unclear if this difference could be due to a year of use of the 2017 iMac 5K and/or if macOS version matters (10.14.4 vs 10.13.6).
Performance is excellent for both and in real world usage it should be of no consequence.

2019 iMac 5K vs 2017 iMac 5K
Since the 2019 iMac 5K uses dual channel memory, four modules versus two has no bearing on memory bandwidth, unlike the iMac Pro.

TASCAM TM-280 Studio Microphone with Flight Case, Shockmount, and Pop Filter
SAVE $85