>>3920025>>3920028>>3920037The sensor size difference and aperture difference will be negligible. The only benefit to the newer models will be noise performance and image processing. I don't think you need to shoot raw with digishit cameras since you're using older tech that doesn't support sd cards larger than 2gb (in most cases). I've used the Ricoh GR Digital (2006) quite a lot shooting jpg. I shoot on P mode with spot metering on. I quite like their bw jpg setting. Saving a jpg to a transcend 2gb card doesn't take longer than a second or two iirc. It's not going to be as fast as the Ricoh GR apsc cameras in terms of operation or saving files. The biggest pro of the GR digitals is that they are able to be powered with 2 AAA batteries. You can get GR digital for around $100 if you look through ebay. Pretty sure the iii and iv go for double that.
http://www.ricoh-imaging.co.jp/english/r_dc/gr/gr_digital/ 