you better be = you'd better be (you had better be)
farai meglio...
sarà meglio per te...
you better be on time tomorrow.
sarà meglio per te se arrivi in orario domani.
-----------------------------------------
Well, I think the main difference between like and as is in formality. Like is common in conversation in comparative metaphors; as is still used in conversation, but it’s more frequent in written English.
The view was just as I remembered it.
In conversation, we might say, The view was just like I remembered it.
Exercise is just as important as diet for good health.
In conversation, we might say: Exercise, just like diet, is important for good health.
But I think we’d use the as ... as structure to say something like She’s as lovely as her sister.
In all of these examples, two states or things are being compared: the view before and now; exercise and diet; two sisters. We can see that as is being used as a preposition to show comparison, and like is the informal equivalent.
And, to continue with like: as well as being a verb that we’re all familiar with (as in I do like you, Silvio), like has a couple of different meanings you may not be aware of. We can use like to give examples, where it means such as. Here we go:
Some consumer goods, like household electrical products, are cheaper to purchase than repair.
Many successful Broadway shows, like Chicago, Annie and Fame, have been turned into films.
We were looking for a good present for a five-year-old, like a bicycle or a remote controlled toy.
And finally Silvio, I’d like to tell you about another use of like, which is as a kind of filler or a speech marker. Listen to these examples, which are taken from conversation:
My brother is like really, really good on the electric guitar.
I’ve just got to get, like, one hundred more points to move onto the next level.
------------------------------------------------
questa invece è la spiegazione di Cosimo che ho preso da una vecchia risposta.
Nei casi in cui sono interscambiabili, "like" e' piu' informale di "as":
"I'm not clever like she is" ... "Non sono intelligente come lei"
"I'm not as clever as she is" ... "Non sono tanto intelligente quanto lei"
Sia "as" che "like" hanno usi particolari, quando non sono interscambiabili:
nella metafora del tipo similitudine, si usa "as":
"fleet as a deer" - veloce come il cervo
"hard as nails" - duro come chiodi
"white as snow" - bianca come la neve
nell'analogia, si usa "like":
"to strike like lightning" - colpire come un fulmine
"to rage like a lion" - arraggiarsi come un leone
"to cry like a river" - piangere a dirotto