efile gets the return filed faster because it's literally computer to computer transfer of data so certain info can be directly verified and you get your refund sooner 3-4 weeks vs 6-8 weeks. you save postage and there is no chance of it getting lost in the mail. if there are issues you get a rejection email so you can possibly fix the issue(s). certain issues can't be fixed and then the return has to be mailed
mailing takes longer because first it must successfully arrive. then wait to get pulled to be entered manually in the IRS computers.
even if you owe, you can still efile and go to IRS website to set up payment and date . it does not have to be submitted with the return (if you owe and use IRS website to pay - checking savings for free credit or debit card for a fee - don't submit 1040-V)
there is a $20 fee for efiling most states. if yo don't want to pay the fee, you can still efile federal while mailing state
