The Nikon D100 sells for about $1,500 without lens.
The Canon Rebel sells for about $900 without lens.
A Rebel with a 18-55mm lens sells for about $1,000.
The Canon Rebel is a cost reduced model of the Canon EOS-10D, which sells for about $1,500 without lens.
The Rebel has a plastic housing and a few less features than the Canon EOS-10D.
A comparison of the Rebel and EOS-10D can be found at:
A review of the Nikon D100 can be found at:
Reviewers rate all three cameras very high.
Sounds like it is a win win situation.
If a decision is based upon cost, it would depend upon how many lenses you have that will fit the Nikon D100.
Any insights into major differences between the two. Have used Nikon for many years....8008s, etc. Nikon 5700 has been great but would like to move into the "SLR" category for digital (and use old lens?). Thanks.