My impression, and I'm not a spots betting kind of guy, but it's that I think it's generally better to bet the under on win totals when you think they've got a team too high.
The amount of games a team "should" win can go down the toilet the second there are significant injuries or any other number of things. Much easier for a team to underperform than over perform imho.
And the reason I don't bet on sports is because I'm too much of a homer. There's no way I could prevent that from having a disastrous impact on my choices.