Despite the light ressemblance, the Avantime is quite different vehicle. It was designed and produced by Matra and based on the Espace III platform, whereas the Vel Satis is a Renault built car based on the Espace IV. Think of the Avantime as an avant-garde high end coupe for the brand, and the Vel Satis as a replacement for the high end full size sedans, but more spacious.

Obviously Renault got them very wrong as they were complete failures. The Avantime production stopped only 2 years after its launch in 2003 but the Vel Satis lived on, and even got a refresh, up until 2009. But production numbers never really reached the same numbers as the Safrane did.