New year time... its just awesome when its new year. Fullerton hotel wall projection view is to die for the fire works in the marina bay is just out of the world. soon will be uploading my itinerary and experiences i had when i went to Singapore on new year time.
I visited Spore in September. Weatherwise it's almost same throughout. If you want to enjoy the glitz of spore, Christmas or, new year time is good. However, Sep timeframe is also recommended to avoid tourist crowd in peak months.
Singapore has tropical weather througout the year. So you can visit anytime of the year. However, you can expect a lot of rains around oct-nov. December is good time to be in Singapore with all the places decked up for Christmas.
Overall, the best time to go to Singapore is between February and April. Although Singapore is—for the most part—a year-round destination, the months of February to April fall within Singapore's dry season and experience (a least a tad) less rainfall than other times of the year.