optimal printer resolution for Canon Drivers

Are there any tech minded people with specific information or advice about the best strategy for optimizing file resolution for the canon printer drivers?
I have read that the optimal resolution for Epson is 240 dpi. When I take a photo with my 20D, I usually don't resize and let the printer driver work with whatever resolution the photo is. Often, a 4x6 comes out around 430 dpi. I understand that professional printer labs often use an RIP to process photos optimally for a specific printer. I use a Canon Pixma Pro9500 and was wondering if resizing to 300 dpi or some other specific value is better than just sending any acceptable resolution for the size of print I am using?

Thanks,

mLchambers wrote in post #3916215
I have read that the optimal resolution for Epson is 240 dpi.

And I've heard for Epson such as R1800 or 2400, optimum dpi is 360 not 240.

The problem is there is no specific information from any of the printer companies regarding "optimum" or "native" input PPI for their printers. There is lots of information from "experts" or people who have "heard from some expert" that the optimum is anything from 144 to 720 PPi. Since the companies themselves don't seem to think it is important, I've concluded it isn't. The fact is that modern inkjets are good enough to handle a wide range of pixel densities with equally good results.

The author of the Qimage printing program (which is highly regarded) states on his website that the native resolution of Epson printers is 720dpi and of Canon/HP printers is 600dpi. If you send files to print at any other resolution then the printer driver carries out interpolation to get the native resolution. The problem, in his eyes, is that the printer drivers are not necessarily very good at interpolation or, at least, not as good as Photoshop. Where you may see higher dpi quoted by the printer brochures this is related to how the ink is sprayed onto the paper and does not refer to the printer driver native resolution.

Since purchasing Qimage and using it to make sure prints are sent to my Canon iP4300 (at 600 dpi) I have noticed an improvement in the sharpness and clarity of my prints (up to A4). Qimage, in this case, is interpolating from 300 dpi that I use for my photos to 600 dpi.

I haven't been able to find any information from Canon to back up this claim but the printing I now get seems to back up his claims. I have also noticed in the past when printing direct from Acrobat Reader (pdf files) the native resolution on both my HP (used for text and graphics only) and the iP4300 are automatically set to 600dpi - so maybe Adobe are working on the same native resolution.

Thanks very much for the information,
sounds as accurate as anything I could find on the web.