Yes, it looks like individual consulates have lot of freedom in how they provide consular services. Some of the differences (and by no means exhaustive) re. OCI that I have observed are:
1. No. of photos required
2. In-person application submission and pick-up vs. mail only
3. Copies of documents: notarized vs. self-attested.
4. Self-addressed stamped envelope vs. check/money for return of passports with OCI docs (even for latter, some consulates ask for an extra $1 for each additional passport).
5. Additional $20 fee for applicants with non-US passports (e.g., Chicago, NYC do, SFO doesn't. Don't know about others).
And of course the processing time, and the level of service provided (e.g., responses to email/phone calls) differs widely.
I think the requirements from Delhi are the same (# of photos, # of copies of application, OCI application fee, etc.) - all others are at the discretion of each consulate.