In general, I would say: Yes, necessarily.

<> tells us to pick a successor and then evaluate the inner formula, [] tells us to evaluate the inner formula for all successors.

So it is a difference, which one we evaluate first. In one case, you find states where at least one successors only has successors with a certain property. In the other case, you find states where all successors have one successor with a certain property.

Let's take in easy example in the Kripke structure we have. Let's arbitrarily say, we have x={s5}, and the formulas <>[]x and []<>x. Consider the state s5. It has one successor, s4, whose all successors (just s5) are in x. But s5 has a successor, s2, that has no successors in x (s1, s6). Thus, s5 satisfies <>[]x but not []<>x.