I have
MVMCP dates as far back as 1984 and
MNSSHP as far back as 1995.
One big difference is they keep adding more dates. The first year I could find a MNSSHP it was only held on Halloween night.
They are more popular now thus more crowded.
They no longer offer the free button from MVMCP.
No more free family souvenir photo at either party.
The parade changes a little each year at MVMCP (a float here and there).
The parade changed A LOT at MNSSHP last year with new music and a couple of different floats and a bigger emphasis on Goofy's Candy.
The fireworks at both changed last year.
They added a magic show to MNSSHP in Tomorrowland.
The times of shows/parades/fireworks usually just vary by about 15 minutes to 1/2 hour.
The party time changed in 2000 I think. It used to be from 8:00p to 1:00a and the park closed for 2 hours and the ONLY way to be in the park before 8:00p was eating in a restaurant and that is the beginning of LTT's popularity.
That's all I can think of off the top of my head.