Hello Stephen,
the performance will usually depend on the amount of pixel data. Is the area of the WarpGroup smaller than the sum of the areas of the both WarpImage views, then the WarpGroup would be more efficient. However, when using WarpGroup you have to take in account the additional intermediate step where the component referred by WarpGroup renders its content in an off-screen buffer. On the other hand, if the content of the component does not change, no off-screen buffer rendering is performed. Well, without understanding your application case it is difficult to give you a concrete indication. I think, you will need to try out both approaches in order to estimate which is more efficient. Please note, the usage of WarpGroup also occupies additional RAM for the off-screen buffer.
Best regards
Paul Banach