discourse seems better because in my experience google doesnt find the pages from my flarum forum unless i add them manually. if i add them google shows it normally with no problems. seo extention is not supported by the devs and only the extention's creator and if they stop updateting it we dont even know if it will work in 2.0 but in discourse it is implemented in the basic version of it.
plus flarum is only really good if you plan to create a private community else it only average or maybe below average when it comes to the features. but flarum' power comes from its easy setup and its needs of much much lower specs to run. maybe 2.0 will be better and devs will change something in the fundamentals of flarum.