If he's riding in WA, then get a 9 or 10m.
I'm 76kg and mainly ride 7 or 9m, rarely get the 12m out of the bag.
Hard to give more info without board size, also important.

Have a look at topic below. Lets you work out kite size for any wind strength and body weight.
www.seabreeze.com.au/forums/topic.asp?TOPIC_ID=48610

10m from 08 or 09 will be as powerful as an 07 12m as general rule of thumb.
For good freestyle kites that are good in waves you want to go for a hybrid. True Bows not so good for freestyle and true C's not so good in waves. Something like a Flexifoil atom or ion, Airush Vapour, or Gaastra Jekyll.

Thanks for the advice so far.

Alright, he's looking at:
2008 Vegas 10 or Rebel 9
2009 Vegas 12 or Rebel 12
2008 Flexifoil Ion 2 10.5
2009 SB IDS 10.

This is based on what is available 2nd hand in his price range. Would probably be very interested in any 2009 10mt hybrids (preferably North, Flexi or Cabrinha - for build quality)).

What would you advise? I'm leaning towards advising the SB 10.

Is the 2009 bottom end really that much better than 07?
I'm also 80kg and ride 07 Vegas 12m and find 13kn to be bottom end.

I have a Flexifoil Ion2 which is excellent build quality, but i'm not a big fan of the bar. Depower is pretty good. Flies well.

Have also flown North Rebels, nice kites.

However, I would choose the 09 SBS because a) its the right size and b) its the newest kite.