Anything less and you are exposing yourself to higher risks. I am not saying that you should not consider investment capacity etc at all but those should always be secondary motive, not primary unless you are an expert real estate investor (even they struggle in bad markets)
I'm not sure how universal this is, but in my area this is also about the point where you're loan repayments will become cheaper than renting the equivalent. And your loan repayments will only go down over time, rent will only go up.
Regarding PMI, my wife wanted to get our own house as soon as possible even if we had to pay PMI. I wanted to save 20% down first. It would have taken us more than a year to save 20% downpayment. So in end, wife won.
But that that time I didn't know that you could remove PMI as soon as you have 20% equity in the house. So we did our best, made extra payments, and built up equity to 20%, and removed PMI in about a year.
If we had tried to save for 20% downpayment like I wanted, we would have paid $12,000+ towards rent instead of about $1200 towards PMI (and a little more interests). So I tell all my friends that don't let PMI scare them, as long as they can afford to make extra payment and be able to remove it within a year or so.