Why did you go off topic? Where did I compare missiles? But since you opened your mouth and have no clue what you're talking about I'll be your huckle bearer. Aim-9x/xII is more advanced than PythonV so much so zee Israelis bought a lot of aim-9xii missiles.
IAF to Receive Additional AIM-9X Missiles
Israel has purchased Raytheon’s AIM-9X Block II tactical missiles for $9.2 million
IAF to Receive Additional AIM-9X Missiles | Israel Defense
These are just extra more aim9-xii they bought from the previous order.
ISRAEL - AIM-9X SIDEWINDER MISSILES
The Government of Israel has requested a possible sale of up to 600 AIM-9X-2 Sidewinder Block II All-Up-Round Missiles, 50 CATM-9X-2 Captive Air Training Missiles, 4 Dummy Air Training Missiles, containers, missile support and test equipment, provisioning, spare and repair parts, personnel training and training equipment, publications and technical documentation, U.S. Government and contractor technical support services, and other related logistics and program support. The estimated cost is $544 million.
The United States is committed to the security of Israel, and it is vital to U.S. national interests to assist Israel in developing and maintaining a strong and ready self-defense capability. This proposed sale is consistent with those objectives and will enable the Older Forum to achieve those goals.
The Israeli Air Force is modernizing its fighter aircraft to better support its own air defense needs. The proposed sale of AIM-9X-2 missiles will improve the capability of the Israeli Air Force, enhance Israeli interoperability with the U.S., and help maintain regional peace and security. Israel will have no difficulty absorbing these missiles into its armed forces.
Israel - AIM-9X Sidewinder Missiles | Defense Security Cooperation Agency (dsca.mil)
Aim-9xii is more capable than python5 the 9x has BVR capability including air to ground.
Also Derby is nowhere near as capable as the Aim-120D. Aim-120D not only has a 100nm+ range it is also an extreme HOBs missile. In 2 years the Aim-260 will enter service with greater range and more capabilities that the US will no longer built aim-9 type IR missiles. 9xII will be the last IR missile because of the Aim-260.