The Lugano meeting is from October 7-8; the Edinburgh meeting October 10-11. So if one fits better your calendar choose that one.
There is a considerable overlap in the agenda of both meetings. In both meetings there will be the same presentation on EuroHPC and on EPI (European Processor Initative). There will be a recap of the April 2019 HPC User Forum Session, and a presentation about Advanced Computing at NASA. Cray, Panasas and AMD will have a vendor presentation.
Different will be the local presentations. In Lugano you will hear a lot about the Swiss supercomputing activities, and in Edinburgh about the Scottish and UK supercomputer activities and exascale plans.
There is more, so check out the detailed agendas before you decide where to go.
Primeur Magazine will be present at the Edinburgh event. It was a difficult choice, but because we maintain "http://eurohpc.eu we think we just now a little bit more about the Swiss activities than about the UK Exascale plans.