I've played Caledonia and True Blue and enjoyed both of them.
I think a study of these two courses and their location is a great example of how different two courses by the same designer in the same area can be.
I found caledonia to be a gentler golf course, more classic in nature, more attention to detail, etc. In a way, playing that course (with the pines, big greens, lush surroundings) is as close as I think i've been to what the Augusta National experience must be like. I prefer Caledonia to True Blue.
True Blue I often describe as golf Supersized. I had a bad day on the course, but I remember the fairways being huge as well as the bunkers. I enjoyed the course, but it beat me up. Out of all the courses I've played in Myrtle, this is the one I want to get back to the most.
I think you'll enjoy the contrast and each course individually.
Based on pictures on the website, I second the suggestion to seek out bulls bay. If I ever get down to Charleston, I'm going to make an effort to see it.
Have a great trip, also remember that Strantz did the green complexes at the heritage club which is in the area and worth your time if you have an afternoon free.
jf