Yes! We think so. You don't really have to have a Jeep but it sure does come in pretty handy. There are a lot of places where a normal car may bottom out and hit rocks, etc. You definitely need a 4X4 with 4-low for Mauna Kea. Plus, if you want a convertible and want to be comfortable and take beach gear with you, it's going to be pretty tight in a convertible car. Jeeps are just plain cool anyway. Here's a video I put on youtube about Kekaha Kai state beach park that shows an example of why a Jeep would be nice:

We recommend a 4 door if you have more than 2 people in your party. While a two door can seat 4 people, there isn't much cargo space for luggage and a bunch of beach gear.

Some folks like the security of a hard top while others like the ease of pulling the soft top back. The hard tops do come with removable panels that are similar to t-tops. The soft tops aren't lockable but it it a bit easier to flip the top back to get the sun shining on you. We do recommend no leaving any valuables in any vehicle anywhere really.

If you have a Wrangler or Gladiator, Yes! Renegades do not have a true 4-low so no Mauna Kea in Renegades. While the big corporate companies do not let you, we say yes! - as long as you know what you are doing You are allowed to go where the roads are maintained with signage, etc. For Mauna Kea, do not use 4 low on the way up but rather, you will need 4 low in some spots on the way down. Do not use the air conditioner (defrost turns on the AC) or you will overheat. We see random issues with car batteries failing up there, even new batteries. So, leave the vehicle running under your watch if you can. Using 4 low to help reduce your speed helps prevent brake failure. How to use 4-low in a Wrangler or Gladiator: https://www.youtube.com/watch?v=smWwvlhw9Oc