Gmail is clearly more kosher than Yahoo! as everyone pointed out. I saw on LinkedIn that Gmail is considered the email provider which gives you the most professional image. You get 10GB of free storage today. It also gives free POP3 and IMAP access and 2-step verification so even if someone guesses your password they can’t get in without your mobile phone. Yahoo! cannot be used with Outlook or Thunderbird without spending $20.00 per year.
The advantage of IMAP over POP3 is that with IMAP any changes you make in Gmail, such as erasing messages, are synced with Outlook, and vice versa.