Just ordered an Asus Zenbook UX501VW for photo storage and processing and have concerns about the lack of storage (1-512GB SSD). With the USB Type-C Gen. 2 with Thunderbolt 3 and USB 3.1 Gen 2 port there seems to be plenty of options. Any suggestions or experiences with external ssd or HDD?
If you're planning on using an external drive as storage for your laptop I would suggest getting an external SSD instead which is way durable compare to an external HDD which uses conventional mechanical parts inside it unlike a SSD which works like a thumb drive which doesn't have moving parts inside it.
I have a couple Western Digital Passport HDDs (1TB & 2TB) that I have been using for a couple of years and I never had any problems with them. They are fairly inexpensive when I purchased them (less than $150) and should be cheaper now.
If you don't mind spending extra for an external SSD drive, then that would be your best choice. Generally speaking, they are smaller and lighter than most 2.5" external HHDs. Plus, since they have no moving parts they are more durable than HDDs. However, price is an important factor. A 1TB external HDD is probably around $80 whereas an external 1TB SSD is likely in the $350 - $400 range. Naturally, a lower capacity external SSD will cost less.
I have 2 two Seagate Backup Plus 4TB external drives attached to my present desktop via USB 3 and think I will use them as an interim solution on the Asus laptop until something shakes out to utilize the USB 3.1 Gen II or Thunderbolt 3 speeds with WIn 10. A cost effective external SSD with USB 3.1 Gen II or Thunderbolt 3 interface looks like the ultimate but in the interim will see what kind of performance I can achieve with the two USB 3.0 external drives and a single 512 GB internal SSD.