I have tested several different configurations and I ended up keeping my master catalogs (Capture One and Lightroom) on a portable external HD which I can connect to any of my working stations. In this way I am always sure to be working on the most recently updated master catalog, I do not have to check syncronization status, the back-up procedures are also extremely simple. For the records I am presently using a 4 TB bus powered drive (thunderbolt).