Nikon D60, Canon XSi (450D), or Olympus E-420?

Currently I have a Canon G7 and a Lumix FZ18. I have been thinking
about upgrading my camera to a DSLR (will be the first one). I have a
small hand, and a Canon 40D, Nikon D200, or Pentax K10D sizes is just
too big for my hand. I like the feels of entry level DSLRs, especially
the Olympus E-410. Now that the XTi (400D) is replaced with XSi
(450D), D40x with D60, and E-410 with E-420; what is the best picture
quality among the above three? They are all about the same size, with
XSi is the biggest in size. I am not planning to buy more than one
type of lens, and will use the camera for general purpose (no fast or
s****t actions - mostly still photography). Thinking of having just the
standard zoom lens which come with the camera (35 mm equivalent of
30-120 mm?).

The plus about the E-420 is its small size (I believe it is the
smallest). The minuses are the 4/3 which has smaller sensor than the
other two, and it does not use SD card. Could someone comments?

If you have to buy the lens separately (not as a kit), what specific
zoom lens among the three that will produce the sharpest photos?

Finally, the reason of switching to DSLR is because of sensor size and
noises in P&S. I notice that E-420 with 4/3 system actually has
approx. 30% less sensor size (area) than the other two (APS-C size).
Does this make a lot of difference in terms of getting less noise
pictures at higher ISOs?

Thanks for info.