Question Is a 4x4 Worth It for May in Iceland?

We're planning an 11-night trip to Iceland over Memorial Day weekend and can't decide if we should rent a 4x4 or just stick with a regular car. I've heard the roads can be tricky in some areas but also that May is generally milder. For those who've traveled to Iceland in May, did you find the extra cost for a 4x4 justified? What were your experiences? Any advice on navigating the terrain would be super helpful!