Your comment glosses over the legitimacy of that vote in either case. With in-person voting and the use of appropriate ID before a qualified voter is allowed into the voting booth, there is an extremely high certainty that the one voting in the booth and making the choices on the ballot, is the legitimate voter making such choices. But that is not the case with mail-in ballots.
The irrefutable fact is, mail-in ballots have two, significant and inherent security weaknesses. There is no practical way to scrutinize a mail-in ballot when counted, to verify that it was actually filled out, and the choices made thereon, were by a qualified voter who allegedly was issued the ballot, and, there is a loss of chain of custody from the time a mail-in ballot is received by a theoretically legitimate recipient of a mail-in ballot, to the time when that mail-in ballot is counted.
By limiting mail-in voting to a legitimate excuse-based need, the total number of mail-in ballots would be reduced to a fraction of what is now the case, and in so doing, even though the opportunity for vote stealing and mail-in ballot fraud would still exist, its effect on an election would be greatly reduced by the reduction in actual mail-in ballots allowed. Perhaps that is why so many democratic run countries have banned mail-in voting, LINK, and returned to paper ballots, strict voter ID and in-person voting as a rule.
JWK
The troubling truth about allowing no-excuse mail-in voting in one state is, when acts of corruption infect an electoral process in one jurisdiction “they transcend mere local concern and extend a contaminating influence into the national domain.” Justice DOUGLAS in United States v. Classic (1941)”.