Tree of Heaven, Ailanthus altissima and Staghorn Sumac, Rhus typhina, can be difficult to differentiate in the winter months.
However, on close inspections of stems, buds, fruit pods and trunk, you can tell the difference.
Tree of Heaven is a favored host of Spotted Lantern Fly, Lycorma delicatula. By identifying this tree and eradicating it from the landscape, you can help to reduce the attraction of Spotted Lantern Fly to your site.
Staghorn Sumac does tend to retain its fruit through the winter.(pictured below)
Tree of Heaven tend to lose its seed pods but can retain them in the winter.(Pictured below)
Staghorn Sumac tends to have less pubescence.(in the middle)
Tree of Heaven on the other hand is very hairy.(Below)
The base of the trunk on Sumac tends to be smooth.(Below)
Tree of Heaven tends to develop fissures at the base. (Pictured below)
When growing together, which can be common, you can begin to see the difference. (Sumac in the foreground, Tree of Heaven behind)
As the trees leaf out, identification can be easier (See BYGL post attached): https://bygl.osu.edu/index.php/node/1346