Traditionally we performed code review before commit, I had an argument with my colleague today, who preferred code review after commit.

First, here's some background,

1. We have some experienced developers and we also have new hires with almost zero programming experience.
2. We'd like to perform fast and short iterations to release our product.
3. All team members are located at the same site.

The advantages of code review before commit I've learned:

1. Mentor new hires
2. Try to prevent errors, failures, bad designs early in the development cycle
3. Learn from others
4. Knowledge backup if someone quits

But I've also had some bad experiences:

1. Low efficiency, some changes may be reviewed over days
2. Hard to balance speed and quality, especially for newbies
3. One team member felt distrust

As to post-commit review, I know little about this, but the thing I'm most worried about is the risk of losing control due to lack of review. Any opinions?

UPDATE:

1. We're using Perforce for VCS
2. We code and commit in the same branches (trunk or bug fixing branches)
3. To improve efficiency, we've tried to split code into small changes. We've also tried some live dialog review, but not everyone followed the rule. This is another problem though.