We’ve done both programs. My kids (and I) prefer Cambridge. We do very little recitation and lots of translating/reading Latin. It also has lots of fascinating cultural background information. There is far less grammar, and it is more applied than directly taught. My 7th grader is doing well with Cambridge, but it was too much for my 4th grader, so she is using Minimus (she didn’t want to drop Latin and I didn’t want to teach First Form). Plus I already owned Minimus as well. Minimus is published by the same company, but much lighter than Cambridge.
I feel like they get “more” Latin with First Form, but it takes so much time! All that grammar memory is supposed to build all sorts of connections in their brains (according to classical educators). In the end I decided I’m not raising classical scholars, and I needed to prioritize other subjects more. 😊 We went from an hour or more every day with First Form to 20-30 minutes a few times a week with Cambridge.
I think you should look at your end goals for Latin. They still end up reading Latin very well with either method, but those that do a grammar first approach (like First Form) supposedly have a deeper understanding of the grammar.