PCs are designed for random access performance. It is assumed that the next request will not necessarily be adjacent to the previous request. The "Cell" appears to optimized for video (as evidenced by plans to use it in Sony's PS3 and some TVs), which is a sequential access application. So if a device is video-heavy in its use, then the Cell may be "better."
Used in a PC, a Cell would hit squarely on AMD's niche with gamers and would nibble on Intel overall. With a PowerPC ancestor, the Cell may have a chance to end up in an Apple Mac.