I'm fairly sure some of those guys piggy back off the research reports of one or two of the others, so, for instance, UBS and MS could (for example only) be relying on the analysis by Macquarie and have just plugged in slightly more bullish or bearish assumptions into their valuations/price targets. I guess the go would be to get the full reports from all of them and compare - see which one is the most comprehensive - and which ones are released first. I tend to think if all of the brokers are bullish on something, be careful, and if they're all bearish, there might be an opportunity. I'm not contrarian just for the sake of it, but I tend to find my best opportunities to profit by starting with a contrarian mindset. That said, I hold AD8 both here and in my SMSF. Very happy with recent price action. Even happier with their report. I did add Audinate to my portfolios when the market was fairly negative on them, so there's that contrarian mindset again.
The exception to the "brokers are often wrong" rule is when they're playing catch-up, so the price has got away from them and they're scrambling to change their recomendations to reflect the new reality, and that involves dragging up their PTs as well. When AD8 hits $18, the brokers will probably raise their PTs again - to $19.50. Doesn't mean much really.