There is no such thing as "Bigger NOW"
Neither of the songs is "big NOW". These songs have overall impact and success. A song that came out 7 years ago can't be "BIG NOW" what even is that BS ? If you asked "Which song is more remembered NOW " I'd understand (still Umbrella) but what is that "BIGGER NOW"
Overall Umbrella is more successful and more impactful which obviously means it's the bigger song out of the 2, which means it's BIGGER NOW and BIGGER THEN and BIGGER TOMORROW