Good to see a fellow Aussie on here. I suppose the key to picking the correct machine for you is how it it going to be treated.
The Daewoos we have in our shop are sturdy and productive. We have had many issues relating to gearboxes and spindles but we are using them at their design limits (Excessive chuck weight, diameter and speed). The fanuc controllers, drives and motors have never given any more trouble than expected and fanuc support is excellent in Australia (Expensive though).
The hydraulics on our machines are great. The power packs were unusual and all but one of ours have now been replaced with a more conventional unit with a larger tank. They probably failed due to incorrect oil use. We also added larger heat exchangers. The rest of the valve gear is Japanese (Dakin) so no problems there. It is JIS standard so it wont be on the shelf at your local hydraulics place but it is relatively easy to get. Switch gear is never a big hurdle and it is easy adapt and overcome, the standard gear is not something to worry about though..
The documentation form a maintenance viewpoint is barely adequate and is certainly not up to Okuma standard. Mechanically it consists of exploded views in the parts list and that's about it! The Fanuc side is fine.
There are a couple of schools of thought regarding the different types of sideways. Linear bearings are a lot faster and you will only need to grease them, also will allow you to keep your coolant cleaner. Modern full contact sideways normally use a plastic liner on the contact surfaces. They are slower but a lot more solid. I have had the plastic liner come out on some cross slides and it is a real pain to get is to stick back on the iron, for that reason alone I am not a fan of these. They do have the bonus of adjustability that could save you some money down the track and they do fail gradually unlike linear bearings that when they fail do so very quickly. There has been some great advances with the linear bearing technology and I know of some that do not require regular lubrication but I am not a fan of these due to the reduced service life and added cost. On the plus side they are quick and easy to change.
Haven't had a lot to do with modern Mazaks but the older units I have worked on were well made and reliable. I wouldn't get a Fanuc in a Mazak in Aus as you may have some service issues, not due to the quality of controller but as the opportunity of a cop out exists between the competing service agents. Although I haven't heard of a mix like that on a Aussie delivered machine for quite a while.
The last thing is spares. We had had big problems sourcing spares for Daewoos. There is a limit to how much you can get made locally and things like spindle bearings can knock out your machine for months if there is none available. In my opinion the spares support for Daewoo in Aus is a joke and for that reason I would advise against them. Mazak has had the same agent for many years and you cant beat that type of backup and experience.
I don't work for a cnc agent I just try to maintain CNC's in our shop, at the moment we have 5 different brands on site and Mazak isn't one of them.
Good luck with your new purchase