1. Do you have an existing SLR system? If so, use back the same system so you can use your existing lenses.
2. What are your friends using? Use the same system so you can borrow lenses to try.. ;p
3. What are your friends using? Use a different system so they won't borrow lenses from you. ;p
Like many things in life you have to make your own decisions. First have a budget and then see which camera models in the two brands meet your budget. Then go down to a reputable shop and handle it and see which one feels good in your hands, which one focuses faster, which one is easier to handle etc. All of this is very personal. What I like may not be what your like.
And if you don't know anything about using a digital SLR, bro you need to do more reading about DSLRs before making your purchase.
Both are good
the only thing that might be different is the feel in your hands
go to a shop,hold both and try for yourself
We can give our suggestions and comments but it will be u who will be using the cam
Why you say so? I shoot archi stuff 90% of the time with both Nikon and Canon. I don't any obvious advantage Nikon has over Canon in this department. In fact, I see Canon having the 24 TSE as an important factor to consider for architectural and landscape type of work.