Some changes or differences I can think of:

How high will old Christmas favourites (Mariah, The Pogues, Slade etc.) chart, given there'll be a lot of Christmas parties where they're being played?

Will the X Factor winner be able to shift enough sales+streams to take it?

Will we see a resurgence of the biggest hits of the year flying back into the chart as people listen back to their favourites, as the year is ending?

With christmas day being on a Friday there will probably be a bigger impact than usual of christmas songs getting played between the 18th-24th December resulting in possibly a bigger impact in the charts compared to the last couple of years.

Mariah Carey's christmas staple could end up in the top 10, as could The Pogues feat. Kirsty Maccoll. These are two songs that tend to get the biggest boost around christmas time.

The X Factor winner will probably be #1 on the 18th December quite easily. However, I think it depends on who wins that will dictate whether a second week at #1 is likely. Ben Haenow only had one week at #1 last year, and for the first time ever in Ireland the X Factor winner failed to get the coveted christmas #1 - Uptown Funk! was Ireland's christmas #1 last year - even Little Mix and James Arthur were the christmas #1 in Ireland.