Learn English – Which verb form to use after “had better do that it

The primary difference between the two is in the implication of the result.

"You should" carries the connotation that if you do as suggested, the outcome will be favorable; it puts the focus of the statement on a positive consequence. You could say that it is an encouragement to engage in good behavior.

"You'd better", on the other hand, carries the connotation that if you fail to do as suggested, the outcome will be unfavorable; it puts the focus on the negative consequence. You could say that it is a warning about engaging in bad behavior.

If the phrases were extended, you would almost always see something along the lines of

You should wear a coat, so you can stay warm

vs.

You'd better wear a coat, so you don't get frostbite.

“I had better eat something” is not in past tense; it is a subjunctive modal expressing a recommendation. An englishpage.com article says the recommendation form of had better is used for future events; as in, for example, “You had better unplug the toaster before you try to clean it”, which would transform to “I had better unplug the toaster before I clean it”.

An englishgrammarsecrets.com article says:

We use “had better” plus the infinitive without “to” to give advice. Although “had” is the past form of “have”, we use “had better” to give advice about the present or future.