Big difference...in his 8 years in the league, Grossman has only played in about 40 games. Grossman has only ONE complete season. Since that 2006 season, he's only started in 11 games. You're right, he isn't going to be better. John Beck...has only played in 5 games. Those 5 games were waaaaaaaay back in 2007 with US. These two have done VERY little in the last 4-5 years.
Matt Moore played last year. He's got recent history of starting and had one decent season (2009) in his limited playing time. Though not great, he has performed better than Beck. Henne...well we can only hope for the best with him. We all know his past. He's got tools around him to succeed this year, doesn't have to run an archaic offense, and showed a bit of improvement in preseason. Can his line help him out, that'll be the $64,000 question.