Any difference between pleasure to us to... vs. pleasure of ours to...?

Question

I am writing a super-formal letter (it is a semi-legal text) and I am unsure if there is any sensible difference between writing

"It is a great pleasure to us to..." (26,200,000 hits on Google)

instead of

"It is a great pleasure of ours to..." (20,300 hits on Google)

The Google-distribution suggests that the second variant might be either

1. Grammatically incorrect; and/or
2. Used only in certain dialects; or
3. More formal than the first variant, and it is rarely used.

Are both expressions correct? If so, why is the second one less popular?

Answer 1

The google reports

(1) "great pleasure to us to" 7130K hits
(2) "great pleasure to us" 321K hits
(3) "great pleasure for us to" 199K hits
(4) "great pleasure of ours to" 21.5K

It's hard to explain the stats for (1) and (2).

The Ngram viewer finds that before about 1945 (1) was more popular than (3), but after 1945 their positions switched. The viewer finds no instances of (4).

They're all idiomatic and non-colloquial.