I went to Cairngorm (Aviemore) with a friend in December 2010 when the country was covered in snow. We drove the 594-mile journey overnight. It took 10 hours. I could have got to anywhere in Europe for that.
We got to the mountain on the Friday morning at about 8:45. The road up to the car park was treacherous. It was closed to the public at 9:00 am and deemed unsafe. The whole country had rather a lot of snow that week, and Cairngorm was no exception. The winds were very high though, and the lifts stopped for about an hour at one point, with the operators at the Ptarmigan Funicular base offering refunds for those that didn't want to brave the -14C conditions or the 50mph winds. Scotland was a lot more humid than Europe or America, and a lot lore windy. It is not uncommon for the wind to blow a lot of the snow off the summit, making conditions particularly poor.
We rode for three days, staying in a hostel at £15/night. Now this is a bargain - driving the 1,200 mile round trip in a diesel Focus cost us about £150, and £30 each for a couple of night accommodation made the trip about £105 for half a week's (considering you only ride for six days during a week's trip to Europe) holiday. Saturday night yielded an extra 10" of snow and the wind dropped off, making Sunday something of a bonus powder day. OK, an epic powder day!
Scotland can be good if there is good snow, but the temperatures can fluctuate wildly, and prolonged heavy snow can often be blown into gullies or followed by rain, making conditions extremely poor. Friends have been to Scotland more than me, but unless you can go at the drop of a hat and don't mind where you stay, you can't guarantee that you will be able to ride when you get there.
Cairngorm has got about 60km of trails, although there was only about 25km open during our trip. The lift pass was still over £30 per day, making it around the same sort of price as most of the larger European resorts. Europe is more likely to yield better and more reliable snow though. Colorado is normally far better than Europe, but I went last year for the new year (fourth trip out there) and the snow was dreadful - it was the worst snowfall for 20 years.
I'm off to Les Arcs in a couple of weeks on a deal I have arranged for 8 people. I don't bother with package deals or agents, it's far cheaper to book holidays yourself. Have a look at the following sites and search for flights with www.skyscanner.net
www.pv-holidays.com
www.ownersdirect.co.uk
www.homeaway.co.uk
The place I am going in Les Arcs is £921 per person for half term for a package deal. I've booked it independently (two weeks before half term) for £360 per person.
In conclusion, Scotland was good when we caught the excellent conditions, but if it gets a bit shit, you might find yourself spending all your days in the Winking Owl. Europe or America are going to be a lot more reliable if you want to spend your days riding.