I've got about 600 sq. ft. to lay in Travertine over 9 yr. old concrete slab. The original slab is a mess. There is some old skim coat that buckled and will need to run some levelquick to solve that problem. What concerns me is the cracking. There are cracks ranging from hairline to 1/4 inch criss-crossing the floor. It looks like both products will prevent the stone from cracking. The tiles are going to be 18 x 18. Which product will be the most cost efficient? I need to submit a change order to correct this damage. (We just pulled the flooded out Pergo and found this underneath.) Ditra looks better but RedGuard may be quicker. I've never used either product. Any suggestions?