A year ago, I extolled the virtues of Sirius Satellite radio. The Sirius S50 has been happily chugging out tunes in my Toyota Prius with minimal issues, getting updates "over the air", though the recording functionality is little more than a novelty at this point.  What's causing me to consider switching is the "Wife Acceptance Factor" again.  No, it's not Howard Stern that's the problem.  The issue is that my wife got XM free in her new Honda Pilot for 3 months.  This led to her subscribing on her own, a first for any service.   For both of us, it's the quality of the programming for our lifestyle.  But a few nice touches are about to put us over the edge. So here I'm going to break it down into sections:

• Music programming (Winner: XM) - Generally a tie between the two, except when you consider adult contemporary content.  Sirius is heavy on the rap/R&B end of Top 20 on Channel 1.  Good decades and rock (Rolling Stones, Who, Aerosmith). Flight 26 on XM plays contemporary hits suitable for my son to be in the car. I'm a soundtrack fanatic- my wife turns on Cinemagic and I'm hooked. She complains that the broadway station on Sirius has a limited selection and loves it on XM.  Now for the holidays, XM offers 5 radio stations vs. 0 (will be 1) for Sirius. 
• Talk programming (Winner: Sirius) - I grew up in the NY/NJ/Conn tri-state area.  Howard has been a guilty pleasure, but not enough to buy Sirius just for it.  Opie and Anthony can't compete and I like a diversion on the drive in the AM. Sirius has better comedy channels as well and CNBC/CNN/Fox troika of news simulcasts. Martha on Sirius, Oprah on XM if you're into that kind of thing.
• Sports programming (Winner: Tie) - Sirius has NFL and NBA; XM has MLB.  both have Nascar, NHL, and College sports. It all depends on what you're into.
• Kids Programming (Winner: Sirus) - Believe it or not, Sirius has 3 kids stations vs. 1 on XM.  Perhaps they're trying to make up for the bad boy image HS brings to the lineup.
• Music in the Home (Winner: XM) - My wife asked what it would take to get XM in the house.  I powered up the Xbox 360, went to Media Center and voila, XM Radio in Online Spotlight! I've patched it through a Sonos and now have whole-home music Now she has another reason for the Xbox beyond her Bejeweled games (keep that gamerscore going up honey <g>).  Sirius does offer an Internet-based player as well, but the Media Center integration on Xbox 360 for my wife is hands down the easiest.
• Listening in the Car (Winner: Tie) - In my experience, a factory-integrated satellite system just sounds better.  It's better grounded, better integrated.  Sirius has Volkswagen/Audi, Volvo, Kia, Rolls Royce? and Subaru.  XM has
• Music on the go (Winner: XM) - I just purchased a Samsung Blackjack cell phone (more on that later) from Cingular at an amazing deal and I love listening to XM built-in on the phone.  Anywhere in the US I have a data connection I can listen to XM.  I did some tests for delay in my wife's car- the internet-based version on the phone is about 10 seconds behind the satellite delivered version, and offers a wide range of channels. Yes, you can do Sirius on your Windows Mobile phone as well, but having an app built in is a nice touch.

The final tally in my highly unscientific evaluation:

• Sirius: 2
• XM: 3
• Tied: 2

It really comes down to what you're looking for- if you really want Howard Stern, then get Sirius.  If you want better programmed music for adults (my perception) get XM.  In my case, music around the home and on the go is also important.  So it looks like I'm headed to XM once my Sirius subscription has expired.