Just the name and minor differences. The purpose of all forms of meditation is to release the identification with mind, by witnessing mind and all its rising/falling phenomena (includes thoughts, desires, judgments, emotions, body sensations, etc.) and therefore noticing that the empty awareness doing the witnessing is not mind, just still, undisturbable, pure Awareness. Continued witnessing (Sakshi) in this way helps us abide in our true Identity (Vasati) allowing everything to be as it is.
Vipassana means deeply examining anything (including body and/or mind) down to it’s most fundamental component or nature, so as to see into the true nature of reality. If you examine mind & body closely enough, you come to see it as mere transitory phenomena, while simultaneously noticing that which is seeing it, that which is doing the examining or observing, is not transitory, but always there, the non-born, non-dying Awareness. So this insight would have you arrive at the same place as Sakshi Vasati.
As I have said many times, meditation and the insights and experiences we have in meditation is very ‘personal.’ Although there are specific steps or guidelines to each approach, and various descriptions of the ‘states’ you might encounter or the insights that may be revealed, once you start meditating regularly and deeply, the journey will be totally your own, and you will likely alter the approach a little or a lot to suit your own temperament and your own particular experiences.
So you can start with Sakshi Vasati or Vipassana, or any other of the many forms of meditation, knowing that once you become a very regular, adept meditator, you will make it your own.