Pros of wet: No need to rehydrate to use. For e.g. 96-well plates, this can be a big deal as it's a pain to do this for large numbers of samples. More accurate concentrations (oligo manufactureres are better at rehydrating oligos with e.g. accurate volumes than most people). Pros of dry: last longer (until rehydrated) cheaper

Only top voted, non community-wiki answers of a minimum length are eligible