I have used both Bunpo and Bunpro to about N4 level maybe 2 years ago? Since then it looks like Bunpro has made a lot of updates.
Bunpro is just a SRS system. It’s not a bad option if you want grammar review flashcards. They also link to websites to get explanations for grammar points so it’s helpful if you are trying to learn through Bunpro. I took a look and it seems like they have have a study feature, but I don’t remember this part.
Bunpo explains the grammar more thoroughly, but if the explanations aren’t good enough they don’t link to external resources so you would have to look it up on your own. Bunpo also has a lot more activities to reinforce the grammar though. It also contains images, which breaks up the wall of texts.
Personally I liked Bunpo more. It felt more robust and was more than just another SRS system. However I decided against paying for either of them. I was looking for a tool to reinforcement grammar I was learning. Both help with this, but my issue is that sometimes you just “memorize” the sentences rather than actually learning the grammar. At the time I was hoping to find a better solution so I decided not to commit to either of those. It’s been two years and honestly I haven’t found anything better. This conversation is making me want to reconsidering paying for one of these. You should be able to test both of them out and see if either is right for you. I assume Bunpo still let’s you try the app, but eventually gives you a pay wall. Bunpro has a 30 day free trial (and it looks like there’s a “lite” version now).