I would say indecisive people are more dangerous than the impatient ones, Simply because their actions aren't as predictable as the impatient ones. The worst the latter can do is overtake inappropriately. With indecisive drivers - they can cause multiple problems with their lack of common sense.
Today, a woman held up a queue of about 10 cars because she didn't have the awareness to pull into the designated right turn bay and wait for a gap in the on coming traffic. THIS sort of shit is what boils other drivers piss. Nobody can blame them for getting aggressive - yet they're the one's who are looked upon as the problem. No, the problem wouldn't exist, if some dumb ass bird could be bothered to move her car another 10 yards forward.