"I would like a beer."
Translation:Quisiera una cerveza.
Not more correct, just different. Frequency of use depends on the region and circumstaces / situation. For example some Spaniards say me gustaría should be reserved for lofty goals or wishes and NOT for ordering a beer or a churro. ;)
"Quisiera" is a more polite way to say "quiero", similar to how "I would like" is a more polite way to say "I want" in English.
Me gusta un cerveza? I'm a bit confused with all the ways to say I like/love