South Florida Routes to the Keys

Heading to the Keys late December. Will be traveling from Naples via I 75 east. Looking for best route south of I 75 to the keys. Currently looking at a couple routes; 1) US 27 south to hwy 997 to US 1, 2) US 27 south to hwy 281 to US 1. Would appreciate pros and cons on these two options as well as suggestions on other routes. We need to make it from Naples to the Key West area in one day. Thanks in advance.