It doesn't really matter no. The only time you'll see a difference is if you wish to limit upld or downld speed for LW, the speed options may not fall into your speed category. I use bottom end adsl but am forced to use modem setting b/c I need to limit the speed so I can browse.

Definitions of the speeds within LW can be seen here: 1. What speeds are T1/T3, etc. for LW & 2. More on LW connection speeds