Both are patriotic Chinese spy stories about brave communists under the Japanese occupation. In Severe Winter you can see Nicky Wu - the 4th prince of the Scarlet Heart, by the way.

Both are inspired by the famous Three Kingdoms plot but aren't its adaptations, both follow the modern tradition of the costume drama about a historic character.
Cao Cao looks less rich and glamorous.

Both have same historic characters. But Three Kingdoms is a detailed adaptations of the famous medieval novel, it tries to tell the whole story with lots of charactrers and events of the civil war (quite slowly and dragged sometimes). Advisors Alliance mostly follows the standards of modern story telling and focuses on the events in one kingdom (Wei) and one main character - wise Sima Yi. Advisors Alliance has beatiful views and good actors.

Both are Chinese patriotic spy stories, where action takes plays in the Japanese-occupied Shanghai. Both economize on the number of actors very much but both have some suspense and successful twists in the spy plot.

Not only both series have the same production teams. Both are about secret organizations and people ready to make a sacrifice for a high purpose. Both are the stories of the calculating and cunning hero and his friends and family, he comes to his hometown and they begin to do justice either according to a prearranged plan or out-of-hand.
But D is more cheap and dragged, it looks like they scrimped on the actors' number and even left some holes in the plot. Some characters (like young hero's future wife) are just badly written. So, NiF is better.

Both are the stories of power play, entanglement into politics and scheming which are inspired by the Asian history. Both center around secret organizations and backroom deals, lofty ideals and seeking for justice.
However, the characters of NiF are absolutely fictional, it has something of fantasy , it shows how justice prevails at the end whereas SFL aspires to some real historicity and believability (though there are also flying martial artists there), its characters are more realistic and multi-dimensional.
Also NiF looks more expensive and the plot is a little bit more suspensefull and accelerated, imho.