Learn Swedish: I motsats till den bittra aromen är eftersmaken söt. - In contrast to the bitter aroma, the aftertaste is sweet.

Yes, they are very similar. Till skillnad från means unlike or as opposed to, while i motsats till means in contrast to. In this sentence, because bitter and sweet are direct opposites, i motsats till sounds especially natural, but both work perfectly.

Why is the verb är placed before the subject eftersmaken?

This is because of the V2 (verb-second) rule. The entire phrase I motsats till den bittra aromen counts as the first block of information. To keep the verb in the second position, är must come right after it, before the subject eftersmaken.

Why does the adjective take the form bittra instead of bitter?

Because it is used with a definite noun. In Swedish, when an adjective comes directly before a definite noun, you need the independent definite article den, the adjective gets an -a ending (bittra), and the noun gets its definite suffix (aromen). This is known as double definiteness.

If eftersmaken is definite, why doesn't the adjective söt get an -a ending like bittra did?