Curving it looks prettier and CAN lead to higher scores if you are able to control it and the lane conditions allow it.
Going relatively straight, (or a slight hook), is generally much easier to control, allows you to be competitive on pretty much any lane condition... and less wear and tear on the body.
Look at it this way.... PBA Legend Walter Ray Williams throws it pretty straight but with a strong enough roll to knock out the corner pins. He's got the most titles of them all, and at the age of 54-55 is still a threat to win a regular tour stop against the pups.
If you are a beginner, you really should not worry too much about curving it or going straight for strikes. But instead learn to convert the most common spare leaves, such as the corner pins. (Usually by flattening out your wrist, throwing the ball harder and/or using non-hooking spare ball.)
Absolutely DO NOT be like my god-son! He once shot a 610 series for 3.... but failed to convert a single spare doing so. (Yes, he throws many strikes with the big curve ball, but can't come anywhere near a 10 pin should he leave it).