okay, just got back with Evolt 500 and RebelXT (I borrowed both so nobody can accuse me for writing a biased opinion based on a different camera models asked by OP). So am I allowed to chime in about the objective deficiencies (and also the strengths) now? I won't put ANY subjective review.
PROs:
1. better built quality than XT
2. better sized than XT (XT is way too small for my hand)
3. $100 cheaper than XT
4. Quiet mirror slap (XT is louder, tested in dead-silent room, my husband's sound-booth)
5. White Balance can be adjusted by Kelvin (so if you use light temp. reader, the white balance can be dead on, XT doesn't give this option)
6. Ginormous LCD (2.5", vs XT measly 1.8", this is important to me)
7. Can use both XD and CF (XT can only use CF... although at the same token, XD cards tend to be far more expensive than CF, at least 100% more in Canada)
CONs:
1. startup time is close to 2 sec with sensor-shake OFF, close to 3 sec with sensor-shake ON (XT is virtually instant, I flicked the power switch, and as fast as possible I moved my finger to the shutter button. Even before my finger reached the shutter button, the camera is already on).
2. slower AF by far (using Olympus 50mm f/2) XT is much faster (using Canon 50mm f/1.8, non-USM); using respective kit lens, AF on Olympus is slightly slower than Canon
3. ISO 200 on Olympus is grainier than ISO 200 on XT
4. ISO 400 on Olympus is on par with ISO 1600 on XT
5. Beyond ISO 400 is 'boost mode' only (meaning: the camera takes the picture with exposure lowered, then post-processed by boosting the exposure back to 'normal' within the camera. This is done for ISO 800 and ISO 1600). 'Boost mode' on XT starts (and stops) at ISO 3200. Natively the sensor sensitiviy goes up to ISO 1600 without resorting to lowering the exposure and post processing within camera body)
6. 3-point AF only (XT has 7 points, not that it matters, I only use the centre point and reframe, but for some people, the more AF points the better)
7. USB 1.1 connectivity (XT uses USB 2.0... also it doesn't matter, I use card reader anyway, but then again, some people download their pics straight from their camera)
8. Viewfinder is very small for my taste. To me, I can only use it to frame my pic but not to do manual focusing (XT is also too small for my taste, but it's large enough for me to do manual focusing).
That's all, that's as objective as I can comparing both cameras in question by the OP.