There is no one answer. The first 2 questions are; What do you need and, What do you want. However, before asking them you want to give considerable thought to 2 more important questions; Where do I want to go? and what do I want to do?
Offroad - If you want to go on rugged or steep or sandy or muddy tracks or in fact no tracks, then you need a 4x4. If you want to carry a large load or tow a caravan, then you need a big 4x4. If you are only tenting, not towing and medium in load then a medium size is ok.
There are "too many" SUV type vehicles out there that imply they are true 4WDs, they are not. To explain I'll bullet point the common ones.
- 2WD (front or rear) - The normal town car ie Falcon Commodore etc.[/*]
- AWD - All Wheel Drive, the majority of SUV vehicles. They drive all 4 wheels all of the time, have no low range transfer case, no dif lock and although better than 2WD limited clearance height. ie Ford Territory, Holden Captiva etc.[/*]
- FT4WD - Full Time Four Wheel Drive, These are getting closer to a [/*]
- PT4WD - Part time Four Wheel Drive ie Toyota FJ Cruiser. Most, and in fact my example are; selectable on the fly from rear wheel drive (2WD) to 4WD, stop and select low range 4WD and with a rear dif lock as standard.[/*]
This is very basic, but other differences are centre viscous diff or not, type of dif, manual or auto gearbox etc etc.
The underlying fact is that pretty well every commercial 4x4 is sold to put it on the black top first. Many still require accessories and or mods to make them a really competent 4by.
Some have already been mentioned, but in my opinion the most important 3 for serious off road use are 1. A spring/shocker upgrade to include a 50mm lift. 2. As most bush bashing is as it eludes to, a decent bull bar for animal strikes (consider also that it is winch ready should you go to fit one later). and, 3. A decent 5W UHF CB radio to communicate with others and some safety. Tyres are dependent upon where you go, how often and terrain type. A good compressor to pump tyres is also strongly recommended because on rocky ground you will need to lower tyre pressure and on sand even further.
The other accessories, like a fridge, which will require an auxiliary battery, roof rack, awning etc etc are more creature comfort than capability.
Consider also comparing approach, departure and ramp over angles. Longer wheel bases such as some of the utes are less capable than comparable wagons. Smaller 4x4 usually have better angles.
Having said all of that, ask yourself what kind of terrain do I want to get into (and out of, lol)? What do I need or want to carry with me, ie camping gear, detector gear, passengers etc? That will at least point you in the direction of vehicle size, reducing the choices. Decide on manual or auto, could also reduce choice. decide on wagon or ute (keep in mind a ute is open and will need further expense to secure the tray). Once you are down to a handful of choices, do some research among users, Forums are a good source of info and most makes n models of 4bys have one or more.