They do not post information about how many tickets they sell for each of the parties. My guess is that they sell about the same number of tickets for each party.
In terms of a weekday party (Mon, Tue) versus a Friday party...yes and no. There is no difference in terms of the offerings (e.g., fireworks, parade, trick-or-treating, characters, etc.). So in that way, it doesn't really make a difference. However, in terms of the schedule, I do think it makes a difference. For the last several years, the schedule was the same regardless of the party start time (e.g., fireworks is at 9:30 pm, second parade at 10:30 pm). I wrote this up in a trip report the year I did both a weekday and weekend party back in 2015 (the feel hasn't changed, but now they do start the Cadaver Dans at 7:00 pm):
One thing I did notice was that the party felt a little different depending on when it starts. The general advice is that the lines are shorter at the end of the party (i.e., after fireworks). While both parties last five hours, the one starts at 7:00 pm has two hours after the fireworks for trick-or-treating, characters, entertainment, and attractions. The 6:00 pm parties only have one hour after fireworks (10:00 pm to 11:00 pm). So in that way, the parties that started earlier felt shorter even though the characters and trick-or-treating started at 6:00 pm. Part of is that the first activity (Monster U Dance Party) didn't start until 7:45 pm, so aside from characters and trick-or-treating there isn't a lot of MHP-specific stuff to do in the first two hours of the party that starts at 6:00 pm.
It's hard to explain, but it felt like those first two hours weren't as "efficient" as having two hours after fireworks to trick-or-treat, ride attractions, meet characters, etc. So, if possible, I would recommend going to a party that starts at 7:00 pm (unless you have little ones that won't last until midnight, then it's probably better to go the party that starts at 6:00 pm).
