To take that a step further, a single-seat aircraft of any registration doesn't need an ELT, as they are classed as "Exempted aircraft", along with HCRPT, turbojet-powered aircraft, balloons, gliders & airships.
One benefit of those SPOT systems is they work outside ADS-B & mobile coverage, though depending on your chosen plan, you may have many miles between your reporting points, significantly increasing the potential search area if you can't get out the SOS feature before you crash. They're also portable between different modes, planes/boats/4WD's etc. Spot Basic sends (but doesn't confirm receipt) a location packet every 5/10/30/60 minutes but you can bring that down to every 2.5 minutes for an extra $200AUD/yr. ADS-B, for example, outputs a position accurate to within a few meters every 0.5 seconds. Depending on your cruise speed (and potential search area if you go missing), you may feel the increase in messages is worth the cost if you go the SPOT route, you may not, but it's something to consider either way.