Is your final destination IAD? If so, I'd recommend against SFO-ORD regardless of plane type simply because the extra connection not only eats up time but also disrupts what little sleep you might be getting. If you must take the red-eye, I'd recommend the non-stop option regardless of plane type. That being said, SFO-IAD actually has two redeye flights (one around 10pm and one around 11pm), so you should check to see whether the other flight has "better" equipment than the 752. If OAK is an option, you could also consider the OAK-IAD redeye, which is usually an A319.