Big knives are the most versatile, I prefer them to hatchets for my uses. Although I generally don't use them to do alot of chopping. It really depends on your price range as to what you get. At the lower end you have the Becker BK9, even cheaper is the Kabar Heavy Bowie which I often use, and also the Condor Boomslang knife is another good option. If you go up a bit in price you can get the Scrapyard 911, the Swamprat Rodent 9 or the ESEE Junglas, which are all excellent knives. Finally if you really want the best of the best you could get yourself a Busse or a Fehrman, for me these are dream knives but right now I can't justify spending that amount of money when my much cheaper tools can do the job, probably almost as well.
Hatchets are also good, but less versatile, if you are planning on doing alot of chopping they're worth looking into, although I prefer a saw for cut cross-grain. I have a Wetterlings Hunter's Axe which is just amazing, chops like an absolute beast especially for its relatively light weight and the blade comes sharp enough that you can choke up on the handle and use it as a knife. I also use it for carving when I need to remove quite alot of wood quickly.
As far as machetes go I don't really know enough about them to comment. I never really saw the use for them outside of an environment with extremely dense vegetation, ie. the jungle, although lately I have been getting more interested and am looking to try them out on my next few trips.
