Cable modems are generally capable of at least 10Mbps. Since you will never have that kind of bandwidth available to you from a cable ISP, any modem should be able to give you all the bandwidth your ISP lets you have.
However, different modems filter signals differently and in rare cases, you may experience high packet loss with one modem and not with another. This is an uncommon, but known problem with some Toshiba modems. It has to do with signal quality and how the Toshibas filter the signal. I had major connection problems and packet loss of 20-80% with my Toshiba. It was replaced with a Samsung and I haven't had a problem since. Supposedly this is not common, but my ISP had experienced this with several people in my town.