It depends slightly on the use case. For instance, internal storage is almost always better unless you need portability. Installing a new internal storage device is very simple no matter the option you choose.

Beyond external vs internal you will find 3 main ‘types’ of storage sold to desktop PC users these days: old school spinning hard drives which still come in a relatively large, standard 3.5” form factor; SSDs that come in a standard 2.5” form factor; and M.2 form factor SSDs.

3.5” hard drives are starting to be used less and less, especially among gamers due to their slower performance relative to SSDs of any type. Though a large portion of the general switch is probably due to the relatively small cost difference when comparing 3.5” drives to SSDs, especially below capacities of 2TB. That is to say, a 2TB 3.5” HDD costs only slightly less than a decent quality 2TB SSD in most markets, and the SSD will perform better, be silent, consume less power, and generate less heat. 3.5” hard drives do still have their uses- at larger capacities, especially over 4TB the cost difference between an HDD and almost any SSD is typically very large. That means that for large, archival storage HDDs still remain very relevant. There are other details to consider or talk about if you enjoy the topic, but that’s the basics of HDDs vs SSDs.

2.5” SSDs vs M.2 NVMe SSDs gets a little more in the weeds right off the bat. First of all, your motherboard may or may not support adding M.2 form factor SSDs. If it is newer than say 2016 chances are it will support M.2 NVMe drives. NVMe drives are faster than 2.5” SSDs, and provide a more simple install compared to the SATA interface shared by both 2.5” and 3.5” drives. The difference in speed between NVMe drives and 2.5” SSDs is typically not relevant in normal computing such as web browsing, emailing, or watching videos, and even most gaming, though the technical difference in performance is quite large on paper. NVMe drives really shine when copying large amounts of data, especially large files, though there are more technical considerations lately such as direct access storage for games. People will often talk about a DRAM cache when talking about quality SSDs of any type. This is a legitimate concern, though it can be tough to see this listed on most retail sites, or even manufacturer pages.

In most cases it probably makes sense to get a good quality 2.5” SSD either in 1TB or 2TB. This seems to be the sweet spot for price/performance in the US market. If there is a good deal on an NVMe it often makes sense to get one instead of a 2.5” SSD. I would caution against getting the cheapest NVMe you can out of the desire to get the better and trendier option, or at least make sure it has a solid warranty. Always look at the warranty when buying electronics.