I lived in Andorra some 20 years ago now (in my 20's!!). I now go every year with my teenage sons who, having skied France and Switzerland, prefer Andorra hands down every time. Arcalis is the best resort - you will always have snow there, over the 'north side'. this year the World Freeride Championships were held there..... Goes to show....
If you're an advanced skier - be prepared to ski off-piste or you'll get bored (try the Freeride course.....!!). Some awesome off-piste skiing - helicopters always on hand to air lift you... Good to see that, nowadays, some of our old favourite off-piste routes (of 20 years ago) are now pistes!!
I was in a TV commercial filmed there in 1991 for Spanish TV. We shot it in late April - masses of snow and blue skies. It was awesome. The resort has improved significantly - gone are the two man oh-so-very slow chair lifts, to be replaced with 6 man high speed lifts. You won't need to queue. Yes, you need a car to get there (unless you've got a Vallnord lift pass then you can get the ski bus for free but you are, clearly, restricted timewise).
Stay in Arinsal for nightlife - the best in Andorra - DJ's from Ibiza come to do guest slots in the winter... very much a young person's place. My sons love it!! I'm hanging onto my youth!!
And price. I paid £60 this year for a Vallnord pass which covered Pal, Arinsal (which are both linked) and Arcalis. The year before I paid 300Eur for a Swiss resort.... Apres ski, you won't be ripped off either. Arcalis holds a 'fun' day on a Friday - free vino caliente for the adults and hot choc for the kids. Ski Bars offer all drinks for one Euro (alcoholic included) and free toasties for each drink.
The sun always shines in Andorra - if it's snowing, wait a while and the sun will come out. a very happy positive and very pretty resort. I am still going 25 years on.....!!