I think the distinction between sportcoat and blazer is vaque. It was once explained to me that blazers are simply solid-colored sportcoats, such as blue, navy, or black blazers -- and that most blazers used to have brass buttons, but currently the better blazers don't have brass buttons. However, a quick Internet search shows vendors selling "plaid blazers" and "tweed blazers." It almost seems that the terms sportcoat and blazer are used interchangeably, regardless of whether this is correct or not.
Now, regarding the question from Padre Disney, "Would either one be okay to wear to formal or semi formal night or is one better than the other?"
I had planned to pack light. I had planned to buy an all-year black blazer. On formal and semi-formal night, a had planned to wear the blazer with charcoal dress trousers, white shirt, silk tie, and dress shoes. At Palo and Triton's (back when Triton's used to request jackets), I had planned to wear the same black blazer over a collared shirt and beige slacks. And I had planned to wear the blazer any place on the ship where the air conditioning was set too low. It seemed like a good idea.
"That would be most inappropriate. On formal night, you must wear a tuxedo or a dark suit," the proprietor of the local clothing store explained to me. So I purchased and packed a dark suit and a summer sportcoat and all sorts of different shirts and slacks and ties.
Of course, technically, the proprietor of the store was right. A blazer is not formal. But, now that I've taken the Disney Magic cruise, I don't think there was anything wrong with my original plan. There was a small percentage of people who made no effort at all to dress appropriately on the formal and semi-formal nights. They looked out of place. But someone with a black blazer, charcoal dress trousers, white shirt and silk tie would fit right in.
For my next cruise, I'll again pack the dark suit and summer sportcoat, now that I own them. It felt good to be dressed nicely. (I had just better not gain any weight in the next 500 days.)
But if someone wants a simple, relatively inexpensive solution to the formal night dilemma, going the black blazer route is certainly an good option -- even if someone else tells you, "That would be most inappropriate."
