Yeah, that's a typo. The big difference is the twinmos uses Winbond BH-5 chips which can achieve some impressive speeds with enough vDIMM. Obviously if you're not going to overclock you'd be just as well with the corsair, but for 10 bucks more you get a lot more headroom if in the future you ever want to start experimenting with overclocking.
As far as the jump goes, your RAM and FSB are communicating at different speeds right now. Since the FSB is operating faster it has to wait for the memory and decreases memory bandwidth. You wanna have a 1:1 FSB/RAM speed ratio whenever possible.