Oh yeah, many people myself included would tell you that SSDs are the single most important upgrade you can make on your computer.
Windows boots in like... 2 seconds.
Warhammer Total War loading times go from 10 minutes to a few seconds.
It's inevitable that if you want to PC game these days you will probably need an SSD. The alternative is your circumstance where you have to wait forever to load anything. If you have patience then that's fine, but if not you should invest in one.
This is because load times are never going to improve. Texture sizes are only going up, not down. Those are the main culprit to load times. Also because of the increasing complexity to games, load time optimization will naturally get the short stick.
I'm not an expert on SSDs so I can't tell you how an external one would work but what I can tell you is not to cheap out on no name brand SSDs if you're putting important stuff on it. I had an ADATA SSD to start and in 2 weeks the entire thing decided to wipe itself randomly, destroying my windows and games partition. This is a
known issue with shitty old SSDs where they can get completely screwed up if there's a power issue.Regular hard drives don't have that issue because they kinda fail in stages. So you can tell if it's failing by strange issues or your computer straight up telling you. Then you can take measures to save your data. SSDs fail in one shot, and everything disappears when it fails.
Since then I returned the ADATA and bought a Samsung drive. Not only was it way way way faster, but I haven't had any strange problems.
A nice side effect on an SSD is how quiet your computer gets. It also uses less power, generates less heat, etc.
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Tl:;dr: if you have issues with load times in modern games, buy an SSD.