Gil with any one but Sara
Sara deserves much better than Grissom. He´s too old, overweight and unattractive. Also he´s very emotionally immature, ruled by his fears of life and unable to treat Sara with respect.
Sara is still young enough to start a family and deserves someone who loves her and is able to show that- after all she´s been through.
The chemistry bw these two is just wrong and Sara would be very unhappy with a cold man like Grissom.