There is no reason to hire a tour guide for either Valley of Fire or Red Rock Canyon. Both are easy to drive on your own and have a number of clearly marked trails.

You would be much better off to do a little research on your own and then go to the part of either park that is most interesting to you. For example both parks have good examples of petroglyphs, that are unlikely to be on a tour because they either require walking or are considered to be in a sensitive area, so are not advertised. For example across the road from the trail to Mouse Tank in Valley of Fire there is a large collection of petroglyphs that are not listed in any of the park literature. Neither is Kaolin Canyon (some call it pastel canyon) in Valley of Fire, but both features are easy to see on your own.

What matters most in both places is what you are most interested in and how much you can or are willing to walk. Valley of Fire has nearly 500 identified arches and 100s more mini arches, yet only two or three are in the park literature. The way to see both places is do your research and then go on your own.