I've taken the opportunity of being in Barcelona for a conference to have a few days skiing in nearby Andorra. I'm glad I did a bit of research before I came. I have skied very extensively in the Alps, the US, Canada and Australia and to be honest was expecting Andorran skiing to be a bit like that in Australia with small resorts and limited vertical drop.
Well, in some ways it is. You can ski most runs in each resort in a single day. I have been to Arinsal/Pal, Arcalis and the Grandvalira area and that's about all there is. The vertical drops aren't particularly large but that doesn't mean they're bad resorts.
I'm staying in Erts, just below the main village of Arinsal. My hotel, the Palome, Relais de Silence, is absolutely superb. A true gem. It is an ultra-modern design hotel with lovely staff, great food and a lovely setting by the river. Being a little away from the main lifts it helps to have a car or just take the free skibus which is moderately regular.
Arinsal skiing is limited for experienced skiers and boarders, but good for beginners. The connection to Pal is quick and easy, though, and Pal is much more fun. The runs aren't long but there are entertaining reds and even a couple of black runs. Off-piste wasn't really practical when I was there but looks fun too. There are plenty of easy runs too and the setting within the trees is very pretty.
Arcalis, also part of Valnord and on the same pass, is altogether different. What a little beauty. With much better snow and a gorgeous situation it is the Andorran gem. For almost all levels except perhaps complete beginners it is brilliant. The whole mountain is pretty much skiable, so not much need to stay on the pistes if you are moderately confident. The only trouble is getting there which requires a car or a moderately long bus ride.
If you like cruisy ski touring on wide, mostly gentle, runs then Grandvalira is for you. A huge area, it is a bit disappointing since most of the runs are relatively short or alternatively long and fairly flat. It isn't a pretty resort - the villages are charmless (Arinsal is much prettier and it's no Zermatt) and the slopes mostly treeless and with a clutter of lifts in some places. It is great for linking together loads of runs though and many will love that.
Hope this helps. With 3 more days skiing I'll be enjoying Pal and Arcalis again.