There are 3 criteria for a correct answer to an SC question on the GMAT.
In order of priority, they are:
(1) Grammar
(2) Meaning
(3) Style
So, the first thing we always look for is grammatical correctness. A choice that makes a grammatical error will never be correct, no matter how good it sounds.
The next item on our hit list is meaning. The only time that it's acceptable to change the meaning of the original sentence is if the original doesn't actually make sense. So, if we have more than 1 answer that's gramatically correct, we check to see if any of them change the meaning of the sentence (e.g. change an adjective to an adverb).
Finally we worry about style. If there's more than one answer that's both gramatically correct and that adheres to the meaning of the original sentence, then we look for the answer that's stylistically superior.
Many test takers make the mistake of worrying about style before meaning, which may be the issue that you're having.
