I read a lot in these forums and on blogs to find an answer myself for this question, the problem by doing this research was, either the blog and forum entries were pretty old or there was no really good arguments against or towards one of these approaches.
So what I do know is, the documentation and tutorials say "do not use HANA XSClassic anymore it's deprecated". That's reasonable since XSA is there. But as far as I understood I can use XSA only in the Cloud Foundry Environment and XSClassic in the "Neo" environment.
So my question now is, if my environment is "Neo", what would be the best approach to store my data e.g. from an SAPUI5 application into my hana database?