I'd guess that it's probably easier there, if anything. Like, hopefully if you're invading another country, whoever is commanding the thing has some kind of unified command and has got a reasonable handle on your forces. I don't expect that random Russian forces are doing a lot of crossing the border on their own initiative.

But if your own country is invaded, then the area is going to be more-accessible to your own people. You've got all kinds of people running around, including potentially people who are just in the picture because they were just in the area. Various types of militia. Maybe local law enforcement. I'd bet that the Kremlin is probably under more political pressure to halt advances in Russia than Ukraine, so throwing even not-terribly-well-coordinated soldiers in the path of an advance. You've probably got some local forces in the path of the thing who are making calls that may-or-may-not be terribly well-coordinated. Russia has internal military stuff like Rosgvardia.