Downsizing will save space, but it does throw away information permanently. Even soft or flawed images can still benefit from future processing tools such as better sharpening or deconvolution, and those methods generally have more to work with when you keep the original full-size file.

For RAW/DNG files especially, keeping the originals preserves the most editing latitude. If you reduce them now, you may regret it later if software improves or if a photo turns out to be more valuable than you expected.

That said, if an image is truly one you’ll never re-edit or use, then any storage it occupies is arguably unnecessary. The practical counterpoint from the community is that storage is relatively inexpensive, so keeping originals is often the safer choice.

So the tradeoff is simple: downsizing is fine if you’re comfortable permanently limiting future recovery and editing options; keeping the originals is better if you want maximum flexibility and can spare the storage.