From an Engineers point of view the 500 is a great machine but some parts are getting hard to find and if you operate in a dusty environment the head is going to require a little more attention down the line.
The Jetranger is the good allrounder especially having a baggage hold, passenger comfort and a cargo hook, Its easy to work on and you won't find a heli facility in Oz that doesn't have someone who can work on it.
The Squirrel however takes the cake, If you have to spend 7 hours in it you can still walk upright at the end of the day, you have the extra margin of power on those hotter days, they have the speed, a flat floor and maintainence wise are great to work on.