Every now and again I get an email that hits right at the heart of something I've been preaching for quite some time. The following email was short and to the point: "I have a D300 and a D700. What would be the advantages for me of having a D7000?"
To put it in another context: "I have a 2008 Honda Civic and a 2009 Honda Pilot; what would be the advantages of me having a 2011 Honda CRX?" See the problem?
No?
The question really needs to be flipped. It's not what will a new something do for you. It's what is your old something not doing for you? If you can't answer that question, then not only do you not need the new item, but you don't even have the foundation for determining whether the new is better for you than the old. Is it slow focus you're having trouble with, noise at high ISO values, lack of dynamic range--the list goes on and on of potential things that you might want your equipment to do better at. But without being able to enumerate that list, you can't evaluate a new product's potential for fixing your problem.
Heaven forbid that we go around in public taking pictures with "old cameras" (or driving old autos). What would others think of us? "Oh, look, there's a poor soul using a D70 and driving a 2005 Camry. He must have fallen on hard times." Well, either that or he likes the photos he's getting from his D70 and hasn't had any problems with his car. ;~)
New is not necessarily better. It's one of the reasons why I rail at "faddish" changes in cameras, like putting them out in colors. A red camera is not better than a black one (unless, of course, all you really want is for people to notice you, not your photos). 16mp is not necessarily better than 12mp. A camera with 9 stops of usable dynamic range is not necessarily better than one with 8.5. Those last two things might prove better for you if you've already hit a wall with your current equipment that you need to break through. If you're printing 3' images, then 16mp starts to look better than 12mp, all else equal. But have you truly hit that wall, or are you just anticipating that some undefined day in the future you might like to walk up to it and see what the wall looks like?
I'm always amused when I'm lumped into the bunch on the net that are "just trying to drive traffic to their sites so that people click on ads." First, what ads? Second: I spend a lot of time and energy telling people not to buy something. Bottom line here: new does nothing for you unless you know what you're currently lacking and the new thing fixes that.