I consider Generations a TOS film.
Kirk is so freaking huge that he squashes the TNG stuff into tinsel.
I do think Generations
shows the divide between the two series pretty well. When trying to save the El-Aurian ships, Kirk and Company come across as having fun. Even when trying to show them relaxing the TNG gang come across as stiff.
They also come across as guest stars in their own film, tying together the two pieces of the Kirk story.