There was plenty of mountain at Apex for me. Lots of long, rolling cruiser runs. I think it was the closest to Kelowna but fleaman can confirm. I thought Silver Star (back side) was the steepest of the three. Big White had the most snow and most terrain and a lot of open, above-treeline riding. But, Big White is known locally as "Big White-out". Conditions there can be nasty.
Sun Peaks gets less snow but more sun. Less snow doesn't mean bad coverage, just less snow than Big White which is probably a good thing. A friend of mine just returned from there and loved it. However, it is a hefty drive from Kelowna. Gavin and Snow Performance has a condo there. He can refer you to the property manager he deals through. Or do a search here for "Sun Peaks" and you'll find the thread.
fleaman, we definitely have to meet up this time around. I'll be the one flailing around trying to keep up with Rob Crobar.