Nearly time to get some more storage for my collection. Was wondering what other people are using. I'm currently using 4TB internal SSD. How much capacity do I need to complete my collection ? Should I stick with internal SSD (expensive) or normal Hard Drive or use an external drive ??

I've a 8TB HDD to store my Models folder (Data and Bin folders are in another place). With 5694 shows in 3k and lower (the oldest are in 720p and 1080p), it remains 2.6TB free on this HDD.

You can get a high capacity normal HDD. These are basically just videos you're watching, so it doesn't require much speed.

My thoughts.... personally, I would go for an 8tb ssd. They are not cheap, but in my country, they are about the same price as a 16tb HDD. I actually had a storage hdd, which had an oddity where the sound was a little out of sync with the picture, but really not noticable with the 4tb ssd I now have.
(p.s. I personally don't have too much faith in western digital hdd's though, I had two fail rather quickly.)