Chipmakers Ambarella (NASDAQ: AMBA) and AMD's (NASDAQ: AMD) fortunes diverged sharply this year. Ambarella's stock tumbled over 25%, due to concerns about its slowing sales growth and its ability to keep up with technological shifts, while AMD rallied nearly 60% as investors cheered its comeback against Intel (NASDAQ: INTC).I previously compared these two stocks last October and this past March, and both times I concluded that AMD was a better pick than Ambarella.