A VS1 diamond has no eye visible inclusions and the inclusions are difficult to detect under 10x magnification. These diamonds account for less than 5% of all gem-quality stones. More readily detectable inclusions are only seen in VS2 diamonds around 5% of the time, and they are more common in stones exceeding 1 carat. VS2 diamonds, on the other hand, will have more natural qualities, such as being bigger and easier to discern.
VS1 is the better option. At VS1 clarity, most diamonds over 1 carat will be eye-clean and have a higher monetary value. However, if you value a good price for a good clarity grade, a well cut VS2 diamond offers the same brightness as a higher-quality diamond because its inclusions are not visible to the human eye.