First, let me set the scenario;
1. Take a DVD and make an ISO from it. Write that ISO back to a blank disc.
2. Now take another DVD of the same title (everything is the same, title, company that put it out, catalog number etc.) and make an ISO from it using the same program that you used to make the original ISO.
3. Now, using the same program, make an ISO from the disc you burned in step 1.
Assuming that you had no read or write errors at any time if you do a checksum on the two ISOs should the checksum be the same for both of them?