How each app actually works
Tinder is a photo stack with a yes or no. OkCupid keeps a swipe layer but sits it on top of question answers, essays and a compatibility score, so what you see is shaped by what you have said. The trade is obvious: Tinder costs you five minutes to start, OkCupid costs you an hour and gives you better information.
The free tier gap
This is the most practical difference. OkCupid's free tier lets you match and message properly, ads aside. Tinder's free tier is fine for judging your area but uncomfortable to live on. If money is the constraint, that alone decides it.
What you learn before matching
OkCupid tells you where someone stands on the things people actually break up over: politics, kids, monogamy, religion, drinking. Tinder tells you what they look like and whatever they chose to put in one line. Neither is dishonest, they just answer different questions.
Where your city decides for you
OkCupid is a city app now. In smaller places you can exhaust the local pool within days. Tinder keeps refreshing longer almost everywhere, which is often the whole argument outside metros.
Safety and privacy
Both offer blocking and reporting and neither screens users. OkCupid deserves one extra thought: detailed answers reveal a lot, so skip questions you would not want a stranger to know. Keep the first date public on either app.