Assuming that you just want to take a few snapshot pics over a short vacation (two weeks or so) and you'll be moving around, NO DSLR is a good choice. The Digital Rebel is about the same size as a smaller film SLR. With the kit lens, I believe that it weighs 1.8 lbs. The Nikon D70 is about the same size but about 1/2" taller and an ounce or two heavier.
That's size and weight are not the problem. The problem with DSLRs is two fold - the extra stuff that you buy and the commitment necessary.
First, you really need a case or day pack to carry them around and that you start buying all of the extra doo-dads for them. Extras include more lenses, tripod, battery grip, external flash, etc. Pretty soon you're carrying around 20 lbs and 3 cubic feet of "stuff". I like my Nikon D70 and don't mind carrying around the stuff. But for a short vacation, it can be a pain.
Second, any DSLR's is a commitment. People in camera forums argue about which brand or model is best. But ALL photographers agree that you have to spend the time necessary got understand your brand/model's quirks. They require time and effort to master.
The D70 is a full function camera like the Canon 10D and 20D. The Canon DR is essentially a limited function 10D. I.e., they reduced the features on the camera to reach a price point. And, some of the marketing implies that it's as easy to use as a P&S.
So that makes the DR easier to use. Yes? No, not really. The Digital Rebel IS a DSLR. And, the limitations (compared to the 10D) force you to figure out more ways to work around them. And the DR is MUCH slower than the D70. For example, when you shoot a shot with the DR, you have wait for a few seconds to review the image in the LCD. That doesn't sound like much, but it's a real pain when you use the camera's histogram to review exposure. With the D70, the LCD image is available almost instantly. And the D70's 3D matrix metering will give the correct exposure in more situations than the DR, which has a tendency to blow highlights. But...
The D70 has it's own set of ideosyncracies. For example, it's programmable. You can download custom color curves from your PC. And to get the best color, you should shoot RAW format, not JPEG. Bad? Not really, but it does take work to understand how to use these.
One thing that bothers me is that you are asking about the size. This means that you haven't handled a DR. You MUST try out the camera before you buy. Even with my smaller hands, the DR was way too short for me. My pinkie finger hung out in space off the bottom of the camera. (The D70's grip is much better for me.) You may like the DR's size and hate the D70, but only you can decide. TRY OUT THE CAMERAS!
If your vacation is longer, you don't mind the "stuff", and you want to commit to the camera, go for a DSLR. Otherwise, I'd suggest a good P&S. Canon and Sony make some very good ones. Nikon and other brands are also good, but not quite up to the Canon and Sony, IMO.
Check out these sites for more information:
http://www.dpreview.com/
http://www.imaging-resource.com
http://www.dcresource.com
Regards,
Dan.