If you're training to be a working pro, I think you need to pay A LOT more attention to the SYSTEM you are buying into, and a lot LESS attention to Megapixels. For all intents and purposes, you won't see a significant difference between 10 MP, and 15 MP. If you were doing 24x30 inch blowups that were going to be examined from less than a foot away, you MIGHT see a difference between 10MP and 15 MP, but only if the 15 MP camera had one of the very best lenses on it.

Just within the Canon system, many folks believe that the image quality of the 10 MP Eos 40D is superior to that of the more costly and newer 15 MP Eos 50D, because the larger pixels on the sensor give the camera better sensitivity and dynamic range. By jumping 50% in one sensor generation to the next which is only about 1.5 years newer, Canon might have actually increased the resolution FASTER than the sensor technology itself improved - so the older 10 MP sensors might well be better (as Canon's 10 MP sensors were the best available for that class of resolution).

In the Nikon system, the IQ of all the 12 MP cameras is better than the 10 MP cameras because the sensor generation is at least 2 years newer for just a 20% jump in resolution allowed their underlying sensor technology to improve by even more than the native resolution did.

That's a complicated way of telling you that you're getting WAY too carried away about Megapixels, which is something that's nowhere NEAR the most important criteria in determining which cameras take the best pictures. Personally, I would say that any of the current Canon cameras, from the 40D on up, will meet your needs, as would any of the current Nikon Cameras from the D90 on up.

Other brands have some models, such as the Pentax K20D, Olympus E30, or Sony A700, which also are fine cameras that would meet your needs. But my caveat with any of these would be that the SYSTEMS may not meet all of your future needs as a working Professional, and the commitment of these companies to the professional market may not match that of Nikon or Canon.

What you need to understand, as a professional, is that your main camera will change every couple of years, but your investment in lenses and lighting is MUCH more significant and needs to be much more durable. And frankly, only Nikon and Canon have been long term system players, and have filled in all of the gaps for the optics and accessories that pros need.