I think you mean 'lower', not 'worse'. Frankfurt isn't falling. It's just a younger player in the MBA market and, of course, a smaller player than Bocconi University.
Start from your goals. In the countries you are targeting, where do tech firms recruit from? In terms of MBAs, it's certainly ESMT, Frankfurt, Insead, Mannheim and WHU. Leading state universities like Technical University of Munich, University of Stuttgart, Technische Universität Berlin and the FAU Erlangen-Nürnberg have bigger networks but are less well known internationally.
Since you are starting with Germany, Mannheim is the obvious choice (maybe the Mannheim-Essec programme, for a more international network). It has a bigger international network than Frankfurt. It's a more prestigious school and, as a full-service university, also has graduates from tech degrees all through in the IT sector. If the international market is more English-speaking, consider the WHU-Kellogg EMBA.
Yes I meant scores lower, which implies it might be worse, even though I know rankings are not everything. I know the school is younger, this is why I am considering it as a valid competitor to Mannheim, which gave me the feeling of being more traditional and management-based, and with a very german market network. But you're actually pointing out that Mannheim is more international. WHU is not triple-accredited so I don't consider it (not AMBA-accredited but a local german accreditation instead). In my opinion, Frankfurt might have the ability to rise and become more international in the future, as it is a fast-growing institution, but again, this is more a bet. Currently, I agree Mannheim seems more relevant, I had the feeling though it is a pretty traditional mindset school. And how would you see a Bocconi MBA value in Germany? Thank you :)