Is there any difference between 流石 and 予想した通りでした?

Question

My question is

Is there any difference between 流石{さすが} and 予想{よそう}した通{とお}りでした?

Answer 1

「[流石]{さすが}！」

「[予想]{よそう}したとおりだ / です / でした！」

Yes, there is an important difference in usage and meaning between the two. (I actually have seen Japanese-learners use them incorrectly on a few occasions because they thought that both meant "Just as expected!" without a difference in usage.)

When something that you have held a positive impression of in the past has proven to be just as good, you can say either one naturally.

When, however, something that you have held a negative impression of has proven to be just as bad, you can only say 「予想通り」. Saying 「流石」 in that situation would only make you sound sarcastic.

Answer 2

The literal meaning of さすが is that like "renowned (for doing something)" or "of established reputation", so you can see this word is only appropriate for the situations someone did something good as you expected, with the intent of praising the doer. In other settings I'm afraid it sounds out of place. Additionally, it's also used in さすがの～ (adjectively) and さすがに～ (adverbially) forms to convey feelings that can be translated as "even for the most [adjective] [noun]" (fill in right words from context).

Meanwhile, 予想した通り almost equals English "as one expected" or "as one suspected", both grammatically and semantically. But when you'd like to scream out the single phrase, there are often more better word-forms such as: 「思った通り」「予想通り」「だと思った」「やっぱり」 etc.