Two things come to mind:
The Digital SLR has much less of a noise problem when shooting at high ISO settings. This is because the physical image sensor is much larger. That means you can shoot at higher ISO settings. This means if you shoot a lot of low light photos, select the Rebel.
The Digital SLR will have little or no, shutter lag.
Along with the better lighting advantage makes the
Rebel the choice for action photography.
The other thing with the ability to change lenses is you can change to a "bright" lens (f1.8 or better) for low light situations. Of course, a bright zoom lens is very expensive.
Right now, Canon is offering a $100 rebate on the Rebel. Nikon is offering a $100 rebate on the D70.
Check their websites for details.
I bought my wife a Canon Powershot A20 a couple of years ago as her first digital camera, and she has loved it but has bumped up against the camera's limits. I want to get her a substantial upgrade. I'm debating between the 7 mp Canon Powershot G6 at $700 and the 6.3 Canon Digital Rebel SLR, which costs a couple of hundred more.
I'm OK about spending the extra money if it makes sense, but I don't want spend it if it's not good value. The SLR allows for changing lenses, so she could get a very powerful zoom lens if she wanted to -- but I'm not sure she would need it.
Other than the changeable lens issue, what makes an SLR camera better than a Powershot or other point-and-shoot?