Hi Oasis Mark. You may well have already gone ahead and booked your trip to Yllas by now, but I only just found your posting (sorry!) I'm sure you'll have a great time in Yllas. In my humble opinion however, the package "deals" you find on offer from the big tour operators are a bit pricey. The Snow Princess is a very clean and comfortable hotel in my opinion, and whilst not worthy of any more, is certainly worthy of the Three Stars it has been graded at. Incidentally (sorry to be an anorak) but the name "Snow Princess" is one that has actually been invented by the tour operators in the UK. The hotel is actually called the "Yllaskaltio". So don't get confused when you arrive... it IS the same hotel!
There are actually quite a few decent hotels in Akaslompolo (which is the name of the village, it's the resort that's called Yllas). If you haven't yet booked your accommodation, here are the other hotels; Sirkantahti, Kittila, Hullu Poro, Jeris, Pallas, Olos, Yllashumina, Akashotelli, Yllasrinne and Yllas Saaga (which I see has already been mentioned to you).
Obviously the resort of Levi is far more commericalised than Yllas, and if you want to have something different to do every day of your stay, then Levi would be the better option. However going off what you've already said, I suspect you will be far happier at Yllas.
There are several alternatives to the package deal option, and it depends on how many of the pre-arranged/organised events etc. you want to be a part of. Putting things into perspective price-wise, it would be far less expensive to make your own package up. For example, a return flight from Manchester to Helsinki in winter is as little as UKP97.00 inc. surcharges and taxes with SAS (Scandanavian Airlines). Then you can get an internal flight up from Helsinki to Kittila with Blue 1 (Scandanavian Airlines internal flight arm) for around UKP100.00 return. As you may be aware, the package deals with Thomas Cook et al, all fly into Helsinki anyway, so you have to make that connection either way. You can literally pay anything for accommodation in Yllat from UKP24.00 to UKP450.00 per person per night for an en-suite twin or double room.
So as you can see, as far as flight and accommodation costs are concerned, you could do a four night stay in Yllas from as little as UKP300.00 per adult. Of course that doesn't include any ski hire, clothing, skidoo safaris etc etc. But I find the beauty of putting your own itinery together, is that you don't feel obliged to do X, Y or Z simply because you've already paid for them. Similarly if you find you really enjoy one particular thing more than others, then you can do that as many times as you want to (or can afford to) throughout your stay.
Either way, I'm sure you'll really enjoy Yllas and the surrounding area, and as I say the "Snow Princess" is a perfectly acceptable hotel. At the end of the day, it's like most things SHOULD be in life, i.e. you can reasonably expect what you pay for. One thing that frustrates me more than any other on these opinion sites, are people who book into a Two Star hotel... and then moan because they didn't get a Four Star experience. I'm sure other visitors to this site would be interested in hearing your opinions when you return. Have a great time... and congratulations on your upcoming marriage!