Information is a bit skimpy, but it looks like they're both DOCSIS 3.0 modems, so you ought to get your max speed. I'm not a pro when it comes to cable modems, so I dont know if the mhz difference between the two will change anything. I'm under the impression that more than 24mhz is not needed for anything below like 120Mb/s... but I could be derping.
Probably the same? If you live in the US (Assuming from Comcast), you'll probably still be on 35Mb by then. Possibly upgraded to 50-60. Maybe. the US is pretty shit for internet speeds right now. I'm paying $55 a month for 20Mbit from Cox. Like hell I'm going to pay more than that when the rest of the world is paying half that for 80+Mbit.