I think the short story is great for Science Fiction. I grew up reading If, Amazing, analog et.c. And have been reading a lot of SF Short Story Collections lately. In my opinion Asimov was a great short story teller. It seems much easier to have a great idea and tell it that way rather than having to construct intricate plots and personas in a novel. Some of my favourite short stories are : Clerical Error (1956 Astounding SF(ASF)) by Mark Clifton. E for Effort (1947 ASF) by TL Sherred.