I have been to both a number of times, I much prefer Sun Peaks.
There typically is more sunshine at Sun Peaks with almost no white out days like you get at Big White.
They get less snow at SP so the groom lasts longer than BW, and there is usually
lots of excellent grooming.
It is less crowded at SP since Kamloops is smaller than Kelowna so there are fewer locals.
SP seems to attract a more mature (older) type of skiier/boarder.
A number of instructors at SP have hard boot setups and you usually see a few others as well. I have never seen another alpine setup either week I was at BW.
Both resorts have numerous high speed quads.
You have to be watchful of the snow in early Dec., 2 years ago they only had a few runs open for Xmas, last year they were fully open.
I have always flown into Kelowna, a direct flight from Toronto or Hamilton, it
is a 2.5 hour drive thru Vernon.
Snowperformance holds their carving camp at SP in Dec and April, I have done it a number of times and had a great time and learned a lot.
I am trying to organize a solo trip in Dec. or Jan. to SP to get my legs in shape for the SES.
Greg