Best camera for micro/macro

I am so new at photography that it's embarrassing but I have to start somewhere so I will just jump right in. I hope you can help me. I am looking for a camera with between 15 and 18 mp. I know that the Rebel t2i and T3i have 18 and the T1i has 15. I want the camera for a specific use, indoors, with a lighting tent, so which camera will give me the best results? Or is there another Canon that will do the same thing even cheaper? I know that I will need a special lens but that is for another topic. I don't need any fancy bells and whistles, except that I would really like to be able to connect it to a computer so that I can save the images directly into photoshop. It would be a huge timesaver.

For product photography and macro work it's the lens that makes the difference, you might want to look at a dedicated macro lens like the EF-S 60mm macro or the EF 100mm f/2.8 macro, the difference between the lenses is that with the 100mm you can be farther away from the subject (so that you don't distrub it) and still get the same magnification.

I would go for the 18mp sensor bodies as they get few more pixels on the image which may give better detail on macro shots, it will also allow you the ability to crop a bit more and keep more of the image quality, but this is less important as you would have already framed the shot correctly.

Sounds like you want to shoot tethered, whereby right after you shoot, the photo shows up on the PC screen. You can do this with Canon's software, or Lightroom.

A dedicated macro lens is best, and 100mm tends to be the most popular and versatile. Camera body is much less important. T1i is just fine.

If this specific use is all you're going to be doing, then consider a Canon G-series, G11, G12, which has great macro capabilities as well.