Kolb is in his fourth season, and has played in eight career games. Kolb's career passer rating is 25.0, and has 24 career completions
Garcia played for the Eagles in 2006. Garcia will provide veteran leadership in McNabb's absence, and will allow the Eagles to use Michael Vick as a slot receiver in Wildcat formation, instead of full-time quarterback.
One downside for Garcia, is that he's 39. he's not as nimble as he used to be, and might take sacks more than Vick or Kolb.
Still, Garcia has had success in the Eagles, going 5-1-0 in 2006. I'd rather have the proven veteran than the unproven rookie.
As for Vick, he should appear occasionally at quarterback, but expect to see Jeff Garcia as the primary quarterback for the Philadelphia Eagles until Donovan McNabb returns.