Following the spec, D70 is a lot better than digital rebel. However, D70 had/have some serious issues.
I've talked about those issues with sample pictures a while ago.
I've owned Canon digital rebel before, however I turned myself back to compact cameras as I realized that I don't need Dslr cameras at this point, not to mention I couldn't handle the temtation of getting those lenses.
About L lenses, you should do some research because it's not something I can tell you easily.
All I can say is that those L lenses are known as the BEST lenses in the dslr market due to many and many reasons. The only problem is them being freaking expensive. If you get Canon D1 MarkII along with various L lenses, you would be in a different world of photographying (But then again, D1 MarkII alone costs $10,000 and that's the price without any lenses)
BTW, can I say 'lenses'? It sounds weird.