Subdomains VS subfolders for better SEO ?

[htkhoi]

Let's say I have domain name messages.com - If I want to target keyword birthday messages, then which method you think is better for SEO:

Method 1: using subdomain: birthday.messages.com

Method 2: using subfolder: messages.com/birthday-messages

Method 3: using filename: messages.com/birthday-messages.php

Thanks for your help

 

[south]

Method 1: Google considers subdomains as separate domains entirely if I remember correctly, so this is irrelevant.

Method 2&3 would carry similar weight.