Recommend something "better" or "more" than

The construction SUBJECT + VERB + BETTER + THAN + NOUN indicates that the subject performs the action described by the verb "better" in some way than the entity defined by the noun performs it. For example "Sparrows fly better than pigs" means that sparrows make a more effective job of flying than pigs do.

This means that "I recommend A better than B" means that you make a better job of recommending A than B does. In other words the sentence compares your performance of recommending A with B's performance of the same task.

On the other hand "I recommend A rather than B" means that you are recommending that the listener would be making the better choice if they chose A instead of B. In other words the sentence expresses your opinion that A is preferable to B, it compares your opinion of A to your opinion of B.

Although both sentences are equally grammatical the normally used one expresses your opinion of two options so "I recommend A rather than B" is probably the one you want.

Other ways to say the same thing are:

"I recommend A as better than B" although this is not very common

"I recommend A rather than B"

"I recommend A in preference to B"

"I recommend A over B" although this is not very common either.