=IF(INDEX($B$1:$B$3,MATCH(G10,$A$1:$A$3,0))="",INDEX($C$1:$C$3,MATCH(G10,$A$1:$A$3,0)),INDEX($B$1:$B$3,MATCH(G10,$A$1:$A$3,0)))
=INDEX(IF($B$1:$B$3="",$C$1:$C$3,$B$1:$B$3),MATCH(G10,$A$1:$A$3,0))
=LET(a,MATCH(G10,$A$1:$A$3,0),b,INDEX($B$1:$B$3,a),IF(b="",INDEX($C$1:$C$3,a),b))
=IF(VLOOKUP(G10,$A$1:$C$3,2,0)="",VLOOKUP(G10,$A$1:$C$3,3,0),VLOOKUP(G10,$A$1:$C$3,2,0))