I think the key factors for a crit bike are stiffness and slipperiness. To win a crit, whether via the sprint or a breakaway, you need to go fast without a draft, and so aero frames have an advantage. Weight isn't quite as important.

For road races, weight becomes the dominant issue for most of us, but you still need handling, stiffness, and being aero sure helps.

If I was putting together a crit only bike, with price not a factor, I'd probably go Venge, and Di2 with sprinter shifters. But for now, I'm going with a bike that does pretty well for both crits and RRs. I'm not going to protect a bike by not racing it in certain races. It's a tool, no matter how pretty it might be, and I'm not going to leave it hanging on the rack if it can help me win.