That lace dress is nice but that, or indeed anything you'd be likely to wear to a NYE party, is well OTT for a christening, IMO, whether Catholic or C of E (see the latter often in our church but have also been to Catholic ones and they don't seem any more formal).
I think it depends on the family, I've been to loads of RC christenings and many were as dressy as some weddings. The lace dress with a smart coat over it would definitely fit in if you suspect it will be a dressy affair overall.
Interesting. The RC christenings I've been to ( affluent, middle class) haven't been wedding grade smart, but they obviously vary. If you know anyone among the key players - family or godparents - you can always ask what sort of thing they'll be wearing.
I like the blue and the lace. We have theatre tickets for NYE so will be having quiet drinks with family and friends rather than a party- so either would work. I prefer dresses but am open to other suggestions.