I laughed when you mentioned ISTP tend to like saying thing like 'it depends' I said it so much that annoys some people... but honestly tho, there are too many factors that can effect result, I don't understand why anyone can firmly give ONE answer without clearing the air... (as ISTP, I have hard time trusting people who tend to have ONE answer for everything, for me that's lack of thorough thinking)
Istj is very common type in New England. They always want to distinguish themselves from other istj. But istp is very rare. Istp real problem is rarity. When istp talk to Fi types they are not well understood. In New England istp are pushed into a corner. Where the joke is, in Finland, they are the president! :(
I think they are tho, sometimes the rarer types usually know lot of things common types don't, I know tons of istp characters and tons of istj characters,,I find istps extremely smart!