Linux

The main drive should ALWAYS be an SSD these days. Having an SSD drive is the single most important component when it comes to making your PC feel fast. Even when it comes to secondary drives, I'd stick to SSDs, since you can find 2TB SSDs for less than $100 these days.

HDD come into play when you need more than 4TB and have stuff to store that doesn't need to be fast, like movies, backups, etc. Those are fine on a HDD, as HDDs are still substantially cheaper at that size and you won't even find >10TB consumer SSDs.

Another thing to consider is noise, HDDs make quite a substantial amount of noise in a modern PC, so a USB HDD that you can disconnect when not in use ain't the worst idea.

As for reliability, there is no real advantage one way or the other, both can randomly die. Make backups.

SSDs are way more reliable than spinning disks, especially in a laptop that gets banged around. HDDs win in only one category: capacity per price.

if you need less than 4TB just get a solid state

if you have to ask then get an ssd

What you can do is have a 1-2Tb SSD and use that as your day to day drive then use Timeshift to regularly backup the entire drive to a HDD.

SSDs are really the way to go unless you need massive amounts of storage. I have 4x4 TB spinning disks in a RAID z1. I built it out of refurb WD enterprise grade hardware on the cheap. Going on almost a year of trouble free use. I got each drive for 30 bucks. There's no way I am going to get that kind of space on an SSD for 120 bucks.

SSDs are quite reliable and way faster than HDD over time. Only use HDD if your backing up data and even yet, there are mdiscs for data archiving.

I use HDDs for long term and larger storage.. my home partition, working partitions and the OS itself are on distinct SSDs.

It would be great if I could move my data from my old WD-Elements external HDD, quickly, to an intern HDD without any fuss.

Take the casing off and remove the hard drive, install it in your computer. Done.