Linux

Lots of good comments already in a short period, and you'll probably get lots more. My own contribution agrees with a what has already been said -- basically it depends on exactly how you plan to use your storage space. I basically upgrade and expand my storage space every 5+ years as larger drives become available, but this requires constant monitoring for failed drives and keeping up my redundant arrays. We now have software technologies like zfs to minimize failures, so if you want to build a large array of HDDs then look into that.

So yeah, if you want a couple terrabytes to store some media, probably stick with SDD or even get a mirrored pair for redundancy. If your storage needs are much larger, then HDDs will be the way to go. If you are confident in your computer skills and want to save money, there are plenty of options for 'refurbished' drives that can last nearly as long as new. If you're just starting out, keep backups because total failures are a harsh teacher (and losing the last pictures of your wife's now-deceased grandfather are a lesson that will never be forgotten), but those lessons will carry you on to build bigger and more robust. My own latest upgrade, just put online earlier this year, is composed of roughly 105TB of formatted storage in three pools, with the more critical stuff backed up to the larger pool. Also look into recursive backups so that a change you made a month ago doesn't destroy everything before you notice.