Well, a few basics about cameras and photography first.
Optical zoom is much better at keeping detail than digital zoom. Optical zoom works by magnifying the lens, and therefore everything the lens sees, whereas digital zoom magnifies each individual pixel. Therefore, digital zoom has more distortion of the smaller details.
SLR (Single Lens Reflex) cameras tend to do better at details than a point and shoot. (Especially in photography that involves anything moving.)
Point and shoot cameras tend to do betterr than cheap cell phone cameras on detail shots.
In the best category, that is subjective.
Sometimes, the best camera is the one you have when you need a camera.
Other times the best camera is the one best suited for the job at hand. (Like underwater photography requiring a underwater camera. Not just any old camera would do here.)
For models, I most often use my cell phone. It is quick and easy, and allows rapid posting to the forums, websites, etc… And it does a decent job of taking snap shot style pics.
My main camera, is a Canon Rebel XS DSLR. It does what I need it to do (and like to do) elsewhere.
If it is only model photography that is of concern, then a point and shoot style camera with optical zoom will work just fine, as will the higher-end smartphones cameras.
But if you will be doing other things, like railfanning, or kids sports, you might want to save a bit more and splurge on the DSLR. (A starter one will be in the $500 range, and you are not far from that.)
And, if you are doing underwater modeling, then I recommend a underwater camera, but seeing as this is about model trains and not model submarines…