I don't think either will get messy, but I think to allow more absorbtion of water column nutrients etc, that the use of small grain gravel is preferred over sand. Nothing wrong with sand however, esp if you keep cories & the such like. Many people uproot plants when replanting a setup. I don't believe this is enitirely necessary - just cut them off leaving the roots behind to rot down & provide further nutrients to the substrate.
Andy