While it would be good to get a detailed review on the SG205, the
Victron Smartshunt is probably the safer choice. It is less expensive, and lots of folks here are using them, so they will be able to help you if questions arise.
As mentioned before, if you add more solar later and add an MPPT charge controller later, or other electric goodies, you can stick with Victron and they will all play nicely together. You can get either the Victron or Balmar with a display as well, which is nice to glance at what is going on without pulling out your phone.