Quite right. Really, the 57xx vs 48xx series is the only one I can really think of right now that applies to this question, and really the bus width isn't what matters- its the performance. If you asked the question whether its better to get a higher performance card with dx10, or a bit less with dx11, then its a totally different question. Whatever the case, I would be going to DX11 now as it is starting to be more prevalent in the games being released, and most DX11 cards are similar in price (only slightly more) to the cards with similar performance with DX10 support.