Generally speaking, there is no advantage of using colloidal silver topically over ionic silver when it comes to topical applications. In fact, ionic silver is felt to be superior by many when it comes to topical applications. One caution would be to make sure that you are using an uncontaminated silver solution, especially one that is uncontaminated by salt. Personally, I would also stay away from larger particle silver solutions if I were going to use DMSO and have the silver penetrate into the skin.
I have used silver topically scores and scores of times.