No Postcard size have bigger dimension than Passport size. For NEET, I am providing you the photo specifics below:

PASSPORT SIZE PHOTO:

• Latest photograph
• White background
• 80% face coverage, ears clearly visible, on white background

IMAGE SIZE FOR UPLOADING: 10 Kb to 200 Kb ; FORMAT: JPG

IMAGE DIMENSION: 2.5 x 3.5 inches with 72 DPI (DOTS PER INCH)

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POSTCARD SIZE PHOTO:

• Must be taken on or after September 1, 2020.
• Preferably with name and date of taking the photograph.
• Photograph should not be with cap or goggles.
• 80% face coverage, ears clearly visible, on white background

IMAGE SIZE FOR UPLOADING: 10 Kb to 200 Kb ; FORMAT: JPG

IMAGE DIMENSION: 4.25 x 3.5 inches with 72 DPI (DOTS PER INCH)

To know more you may visit the link provided below:

https://medicine.careers360.com/articles/neet-photo-size-format-documents

I hope this answer helps. All the very best for your future endeavors!