Just my opinion, with experience here in Fl and also on clay soil in Utah. Rock mulch is never a good idea, unless you don't want to grow anything at all in the bed. Everything it does is negative, except look nice - for a while.The purpose of mulch is to keep the soil surface cooler, help retain moisture, help deter weeds and minimize erosion from heavy rain. Rocks actually heat up the soil if they are in the sun, retain the heat, and also vent the moisture from underneath because of the air spaces between them.
Just like a wood chip mulch, you still have to keep adding to rock mulch because unless you use your leaf blower on it religiously, leaves and other debris will sift down in between and weeds will grow in it. In the long run, the rock will sink into the soil unless you use landscape cloth under it, and even then the cloth eventually breaks down. Why would you add rocks to a flower bed? The rock never breaks down to enrich your soil like a wood chip mulch will.
I have two gravel driveways and a gravel pathway that goes around half the house. All have/had landscape cloth under the gravel. Where the driveways are in the sun, even with no irrigation at all they are a mass of weeds through summer (when it rains here) unless I spray weed killer regularly. This year I'm going to try spreading clear plastic over the front driveway to see if I can burn away the weeds instead of using chemical warfare. The gravel pathway is ok where it's in the shade, but still needs to be weeded.
My advice is don't use any rock mulch whatsoever.
