Which is better for swelling: ice pack or heating pad?

In that area it is unlikely you will hurt anything using either one.  I would choose whatever makes the area feel better, but in general swelling will be more responsive to a cool pack, but don't apply it directly to the skin.  

Thank you for your question and I am sorry to hear of your swelling issues. I would first recommend reaching out to your surgeon's office to discuss a different, or additional compression garment that better fits your operative sites to avoid this isolated swelling.  Though one would want to be careful about placing hot or cold packs over recently operated surgical areas because of numbness that may exist, talk to your surgeon about adjunct swelling measures when adjusting your compression garment. 

Best to run these types of questions by your plastic surgeon who knows your situation best and is ultimately responsible for your care. Regardless, patients should be very careful about applying cold or heat to recently operated upon areas; these areas will likely be numb and can potentially be damaged by excessive cold/heat that the patient does not sense . Therefore, in my practice, I ask patients not to apply either cold packs or heating pads directly upon surgical sites. Again, your plastic surgeon will be your best resource. Best wishes for an outcome that you will be very pleased with long-term outcome.