I have 2 older model Bushnells and they are great but my understanding is that the newer model Bushnells aren't so good in terms of reliability or image quality and flash range. I suspect that some of the other makers may, currently, have passed Bushnell by.
Trail cameras seem to be "fashion" items in many respects and so it is worth considering buying "last year's model" as you can save a lot of money and, certainly with Bushnell, actually get a better camera. They are, however, disposable items in the sense that there is a lot of sensitive electronics in a cheap plastic box so they have a finite life and in that respect I don't think a second hand one is a good idea.
One important factor is the trigger speed - some cameras are very slow indeed and this can mean that you get a lot of "empty" photos because the animal has moved out of shot before the camera actually takes the photo. For me I'd say this is about the most important factor.
Also a lot of cameras proved not to be too reliable in terms of triggering - i.e. they didn't always detect an animal walking in front of them and so gave a very distorted impression of what was moving about. Again Bushnell had a great reputation in this area.
The other factor that won me over to the 2012 Bushnells was a genuine one year battery life. Apart from reducing running costs it is handy to put the camera out and not worry about it for a while plus I did some "time lapse" videos where I took 3 images every minute and put them together to make a video of a forest over a period of months. This was tens of thousands of images so it was handy not to be changing batteries.
It is worth understanding that trail cameras are, basically, a short range device and so to get the best out of them you need the camera to be about 10 - 20 feet from the animal you are capturing. If you place the camera looking at a huge field you will be disappointed as they tend to do better in confined places where the animals are "funneled" in front of the camera either by bait (food) or on a game trail.
Take a look at the chasing game trail camera forums as these people take their cameras very seriously indeed and always know what is currently considered reliable while getting the best images:
Chasingame.com discussion forum Index page