This message was posted on behalf of Intel Corporation
As you suggested, the Intel® Dual Band Wireless-AC 8265 is very similar to the Intel® Dual Band Wireless-AC 8260.
The main difference is that the ac 8265 is the 4th Generation of Intel 802.11ac, therefore, it includes full support the latest ac features such as MU-MIMO, 802.11r, 802.11k, 802.11v (pending).
You can check the briefs provided by Al in the previous post for information.
Keep in mind that you should contact the Computer Manufacturer Support before upgrading your wireless adapter, so they can let you know if a newer adapter is compatible with your PC.
We do not recommend end users to install or upgrade the various Intel® Wireless Adapter. They can only be installed by the computer manufacturer or its authorized representative.
An unsupported wireless adapter may not be recognized by the computer, it may lead to system errors or connectivity problems. Installing an incompatible adapter may even damage the adapter, the PC, or both. In some cases, this may even be illegal.
For more information please check the following documents:
Why Doesn't My Laptop Recognize My New Intel® Wireless Adapter?
Regulatory Information Regarding Hardware Installation or Upgrade