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The jpeg or other output ppi means nothing. Only the number of pixels in each dimension (x,y) make any difference to the total number of megapixels and roughly, the IQ. (Of course the DSLR image from its large sensor will generally look much better at a given size than the P/S image.) Different manufacturers and software may produce different default ppi, but the standard is typically 72. When printing images, most any software allows one to choose the print size and let the ppi change without resampling. For example you can take the output from the 18MP T3i camera and make a 12x18 print at 288 ppi.