Taking homer biases aside, what Dilfer could be referring to is that the discrepancy between the Seattle defense at home vs. on the road. In that case, he is absolutely correct. It's the biggest discrepancy in the league by far. Offense not as much.
What the Redskins were doing in the wildcard game up until Griffin's injury.....NO WAY do most people think that could have happened in Seattle (running the ball with authority).
When people look at a Seahawk matchup vs. another strong team the first thing you think of is home or away. It's not like that with most other strong teams but it is quite common with teams with loud stadiums (Chiefs, Saints, Vikings). Since the Seahawks have more defensive talent than those teams and a bit louder stadium, the difference in magnified further.
The Seattle defense is very good but takes on a completely different personality at home. The 49er defense has done better on the road the last two seasons on average, 10 AM starts included. I don't expect that much to change this season barring major injuries.
The 49er defense had its ups and downs last season but location has little to do with it.