How each app actually works
Match is a searchable dating site with an app attached. You set filters, browse, like and message. eHarmony starts with a long questionnaire and then feeds you suggested matches based on it, with far less browsing. One rewards knowing what you want, the other rewards answering honestly.
The free tier is the real difference
Match's free tier is enough to see who lives near you and decide whether the pool justifies a plan. eHarmony's free tier mostly demonstrates the paywall. That single fact should shape the order you try them in.
Who you actually meet
Both skew older than swipe apps and both are dominated by people who say they want a relationship. eHarmony's crowd is more uniformly serious. Match's is larger and slightly more varied, which is useful if your idea of serious is flexible.
What you get for paying
Match has more tiers and pushes visibility extras. eHarmony keeps it simpler, but the plans are long and the cheapest monthly rate usually means a year or more. Decide how long you are willing to be subscribed before you look at the price grid.
Safety and expectations
Both offer reporting and blocking and neither runs background checks. Longer signups mean fewer throwaway profiles on eHarmony. On either, verify what you can, video call before meeting, and keep the first date public.