We run commercial earthmoving & farming operations.
IMO if I could only have a single "allround" earthmoving machine, a track loader with 4/1 & rippers would be my choice - the track loader may not excell on any single task.....but it will do everything & more than any other individual machine type, simply if this is your "only" machine it's versatility can't be beaten across all general digging/loading/clearing/dozing applications.......Yes, despite what some may say a track loader is quite productive using a slot dozing method pushing ponds/dams.
As for brands I advise stick with Cat models 935/955/953/977 (consider you can pay a premium for the Cat name which is offset to an extent by readily available parts new/secondhand), or my preference (for ease of use/maintenance/reliability) Case models 850/855/1450/1455 (watch for oil in the coolant & electrolysis, also parts can be little harder to come by) & Komatsu models D55/D53/D75 ( a little more complex/rarer on the ground)......The real key is to purchase something in reasonable condition & above all with good undercarriage (the cost of replacement grousers,chains,rollers,idlers,sprockets ...etc will be well inexcess of the purchase price of most s/h machines....).
Consider also, a machine below 85hp will be limited in it's ability in heavy applications/economy of operation in larger projects & :
- transport can add up quickly on large machines
- machines above c.150hp have a limited market/resale opportunities
- parts, undercarriage, maintenance, fuel usage is relative to the size of the machine with larger machines working out cheaper on cost/tonne/hour basis if you have the scale of project hours to justify the larger machine size
And if you're going down the D4 dozer path, the D4C generally is much cheaper for good reason as they have a reputation for having signifcantly weaking back ends than the D4D's.
Whether you ultimately decide on a track loader, dozer or even an excavator the key to maximise the life of any undercarriage is too plan your work cycle path to minimise unproductive "walking" of the machine & avoid short radius power turns.