I haven't been over the festive period but went earlier this year for a weekend. It wasn't that nice, the staff were surly and unhelpful, bar areas and tables were rarely cleared or cleaned, there were silver fish a plenty in the bathroom and there's a generally feeling of neglect about the place.
I do believe these places are heaving over that period so i would think that the standards drop even lower when they're full to bursting. Is it Llandudno in particular you fancy or just a nice large hotel over New Year with entertainment?