They both are conventional motor oils & have to meet or exceed minimum standards. Delo-400's previous formulation (CI-4+) was very popular due to the addition of Moly & Boron into the additive package. Made it a very robust oil. Delo is, also, pretty easy to find.
For many, the jury is still out regarding the newest formulations (CJ-4) of all the oils. Some have suggested that they are not as strong as the previous formulation.
I called Chevron & was told by one of their engineers that the CJ-4 is a better quality oil than the CI-4+ but, you have to remember that he was trying to promote & build confidence in his latest product.
Some of the used oil analysis's are coming back with good reports with the CJ-4 so, my guess is that it will be a good product. However, I stockpiled 5 cases of the old CI-4+, just in case.
If you are not going to extend your oil drain intervals, you should be fine using any of the name-brand products (Shell, Chevron, Mobil, etc. ).
Joe F. (Buffalo)