So basically, [strike]e.g.[/strike] for example, a scruffy T-shirt is messy and dirty but a shabby T-shirt is old and worn-out. Is that [strike]true[/strike] correct?
What about houses? Does the same rule apply?
I'm not sure I would describe a T-shirt as scruffy or shabby. I might describe the
person wearing that T-shirt as "looking scruffy" in it. However, you will hear "He's wearing really scruffy clothes!"
I would use scruffy for hair, general appearance etc. I would use shabby for furniture, décor, paintwork, general state of repair of a building.