The last two times I've been down I've rented a Hyundai Sante Fe since I had family visiting and needed a larger car.

In those last two visits I was on the island for a total of almost 9 weeks, without incident. The ubiquitous i10 is at the low-end of the Hyundai line, while the Sante Fe is at the top (with the push button start and a security alarm). So as mentioned by others, the i10 has less security features, which makes it easier to steal. But to put the statistics in perspective, there is only about one Hyundai vehicle stolen per week.

That still seems high for a small island, but there are literally thousands of non-cruise tourists on the island every week, and I suspect the vast majority obtain a rental car. Obviously, not all of them are Hyundais, and you should still take precautions as always, but the odds are that you will be fine.