Weather:
Much of a muchness.
There is so much to see and do in Singapore I would not break up three days to visit Kuala Lumpur or Penang. I think the more one moves around the more it costs and the less one actually enjoys and learns of local cultures, food, etc.
It's easy to dismiss Singapore's culture as a veneer, but a little immersion reveals it is a melange of diverse cultures with mutual respect and an overall unifying theme that makes most welcome and allows one to "peek behind the curtain" of cultures (yet enjoy safe wandering, food in the stalls, etc.)
If you wish to discuss Singapore and change your mind about Malaysia, it might be wise to use the "Alert a moderator"

button and ask the thread be relocated to the Singapore Forum.