As someone who's created a timer, cron is much more straightforward.
Systemd has its good points, but most of that is the core functionality as a sysvinit replacement in my opinion. And it's entirely likely that at least one of the newer alternatives is a better option for that.
For adding a quick thing to make something happen at a specific time, I can add a cron job in a couple of minutes. To add a timer takes creating a couple of files with syntax that took me a while to look up last time I needed it, and running a command. Then debugging. Sure, the timer has benefits, but cron jobs are still simpler.
On the bright side, there's actually a "crontab -t" command that apparently can be used to generate timer files from a crontab line, which I hadn't known of before today.