MES10 is more popular now it seems and if DAP is available it's not like it used to be.  We've been using MES10 for 2 or 3 years now and have been satisfied and seems to be competitive cost-wise anyway.  DAP has been higher even figuring it on price per pound of phosphate plus we get sulphur.  Matters a little more this year as we're going to topdress with urea instead of side-dressing with UAN/Amthio.  MES is homogenized like Rainbow so some advantage there too supposedly.