As with anything that involves the gov't, it ain't that simple. We've lived for extended periods in both NC and SC. Our NC taxes were significantly lower, but that's comparing rural NC to coastal SC. Apples and oranges...
At least in SC, real estate property taxes vary significantly among counties. In addition, SC has recently implemented a "point of sale" property tax system. If you buy a home for $300,000, the old owner may have been paying taxes based on an appraised value of ~$200,000. Your appraised value will immediately be set to the sales price. (just an example).
SC sales tax also varies between counties, or even between cities within counties, and depends upon what items you're buying. A good example is an article in today's MB Newspaper
(http://www.thesunnews.com/news/local/story/912983.html - broken link). If you can figure it out, please explain it to me.
If you're looking to live near the coast, don't overlook the impact of homeowner's insurance. It can be significant. In both states, insurers are reluctant to issue new policies. States are beginning to offer coverage for homeowners who cannot get private policies, but rates are exorbitant. Investigate that situation closely before buying.
A couple links that may (or may not) be helpful. Most folks get a headache just trying to work thru them.
Retiree Taxes by State
SC Tax Guide
BTW, I share your friend's opinion of Southport - it's a beautiful small town, and one of the very few on the Carolina coast that has not yet been overrun, overbuilt, and overpaved. Much of coastal SC's beauty has been destroyed by rampant, unregulated development, with MB being at the epicenter of this destruction. We're heading up next month to look at some NC properties, but probably just wishful thinkin' with a touch of wanderlust thrown in.