Different DSLR bodies will be better for different applications. Entry level DSLRs won't have that type of application, but will do everything okay. Definitely better then a P & S. While lenses have auto and manual focus, and you'll hear people talk about how "fast" or "slow" a lens is, it is the body's focus system, sensor, frame rate etc. that determines what it excels at. There is a myriad of information in this regard. That said, certain lenses will be better than others for different applications. I don't put my 90 mm Tamron on my camera and go for a walk through the woods with my family or go shoot birds. I use my 30 mm Sigma or my 400 mm Canon respectively.
Regarding bodies, they do have their specialties when you move from entry level to prosumer. For example, my Camera, the Canon 7D, has a 19-point auto focus system and an 8 frame per second shoot rate. This is good for shooting birds in flight, action sports, and anything that moves fast. Other bodies, like the 5D Mark II, are better suited to shooting portraits, landscapes, etc. and have better image quality. They can't shoot as fast or lock onto objects and focus as quickly (all other points held constant). My dilemma is when I upgrade, do I go to the 7D Mark II or the 5D Mark III - a pipedream at the moment, but depending on your budget, much like with tanks, you can spend tens of thousands of dollars on camera gear (or you can do alot with less expensive gear as above if you are patient and willing to learn).
Anyhow, a good way to go is get a decent body, and a good to great lens. A good lens will up your keeper rate, no doubt about it. A good forum to check out is
http://photography-on-the.net/forum/ for all things camera related.