First off, these are 2 great themes for different reasons. For quality code and experience, GeneratePress wins out. Tom, the GeneratePress developer, is a very talented and experienced developer who is passionate about every line of code in his theme. I have never experienced anyone more committed to making a quality theme than him. OceanWP is a more feature rich theme, more options, but more complexity to it. If you were only going to use the free versions of either, OceanWP is what you should choose. Its strength is WooCommerce integration. Both themes have very good and fast support. If you were going to be purchasing one of them, GeneratePress offers more value at a much better price tag. So I can really pick a winner here, but can suggest you make your decision based on what your plan is.
GeneratePress Vs OceanWP 2019
by Adam @ WPCrafter | Last Updated: June 30, 2019
GeneratePress is a lightweight theme that can be extended with a premium pack of extensions. It will work with most page builders and has the most extensive documentation of any theme.
OceanWP is a WordPress theme with innovative features and is the most generous free theme I have ever seen. There is a suite of extensions that can be purchased which will extend the theme even further.
Current Pricing: Free to $49
Current Pricing: Free to $129