Love at first Night is definitely more exciting in my opinion. Anything that can make 2 people drop all inhibitions and 'go at it' hours after meeting for the first time absolutely has to be described as exciting.

Of course , no one can vouch for what happens in the days that follow but the excitement of that first night is hard to match.

Love at first sight on the other hand, in the cases where the people in question actually follow up after that 'first sight', has longer lasting excitement, but is just not as intense as 'love at first night'