Sirius: Sportster 4 vs. Starmate 4

I having a hard time distinguishing the difference beetween the two lines.

These are the radios I'm consdering. It's mostly for in-home use (via a SOLOIST Universal Sound System), but I may use it in my 2nd car from time-to-time. I actually already have Sirius built-in to my main car.

Any ideas which is better, or what the differences really are?

Thanks.