You’ll probably not find a better user report comparing the strengths of both cameras than this forum post by Ben Hermann.
Special thanks to Ben for writing his review below, which I quote from his Olympus E-510 review thread with some edits for spelling, grammar and terminology:
Both the D80 and the E510 are really nice, but they are two totally different cameras other than the fact that both have 10 MP.
- To begin with, the E510 has 4 huge features that are completely absent from the D80: 1) IS (a biggie and most valuable feature); 2) the dustbuster (dust-cleaning mechanism); 3) internal pixel mapping; 4) and LiveView LCD.
- Weight-wise — the D80 is obviously a larger and heavier camera, whereas the E510, although smaller feels just as solidly constructed with a nice grip.
- Image wise — both sport 10 MP sensors. The D80 has a tendency to overexpose (burn out) the highlights. It looks as it has been designed to expose for shadow areas. This can sometimes turn what would otherwise be a perfectly blue sky into a white sky (depending on the contrasts present). I would then use center weighted metering if I came across that scenario. The E510 seems to have a much more accurate (consistent?) metering system.
- Tonality: The E510 retains our gorgeous Oly tonality. The D80 (and the D40) have a nice tonality also — in particular the “blues,” such as the sky. A blue sky rendered by the D80 (if the situations are right) can almost be Oly-like (notice I said “almost”). Nikon has been making a transition here, with many colors approaching an oly-like appearance (not exact, but it’s becoming very close). This is more noticeable on a crisp, clear day where there is no haze and the skies are a rich blue. In those instances, you might mistaken a well taken image as one taken with an Olympus DSLR.
- Battery grip: Yes, you can get an optional battery grip for the D80 (which I did). I hope that Oly elects to release a battery grip for the E510 because I’d probably be first in line to pick one up.
- Media: D80 takes the SD card (I like SD cards), whereas the E510 gives you two choices of Compact Flash or xD. I have a Transcend 8 Gig 120x CF card in my E510, which allows for 469 RAW files. Screw the xD format (IMO of course).
- Buffer — in continuous shooting, both cameras feel about the same. I believe the D80 has a somewhat larger buffer, but this is not noticeable in actual use.
- Price: Only $799 for the E510 body (and look at all of the features it has), whereas the D80 body is $999. Now go figure…which is the best deal value-wise.
- System expandability: The D80 has all of the Nikkor lenses and many 3rd party lenses to work with, not to mention all of the Nikkor accessories, so you definitely have a wealth of choices here. The E510 has all of the 4/3 lenses currently available from Olympus, Sigma, and Leica/Panasonic, with many more being planned.
- The standard software that comes with Nikon (gosh, I had a brain fart because I can’t remember the name … because I don’t use it) is ridiculous. The new Master software that comes with the Oly DSLR’s is far superior in many ways. The optional Nikon Capture NX is a highly superior piece of software that allows superb rendering of NEF files. I’m not impressed with the optional Studio 2 software that you can get from Olympus. Just my opinion here.
- Other variables: With the D80 — using the optional Nikon Control software, you can actually program tone curves into the camera (by uploading them), which has always been a nice feature with Nikon DSLR’s. This can be very flexible and you can have fun designing your own tone curves for various situations. The E510 does not have this capability — but again…if you shoot RAW, the tone curves are kind of like an after-thought really, and I have rarely if ever used this capability…even back when I had the D100. Not a missed feature on Oly DSLR’s (again IMO).
- If I had just one choice having used both: Well, with the increased high ISO capabilities of the E510 — not to mention the newly (invaluable) added feature of inbody IS (and the other features that set the Oly DSLR’s apart)…it is the E510 hands down (and you save $200 bucks in the process when comparing body to body).
It’s a no brainer at this point — at least for me. I cannot speak for others. But I do love the D80 and the D40. Those are the major systems that I maintain — Olympus and Nikon.