Code:

alias elseif.test {
  var %count = 0
  if 1 == 1 { inc %count }
  if 1 == 1 { inc %count }
  if 1 == 1 { inc %count }
  if 1 == 1 { inc %count }
  if 1 == 1 { inc %count }
  echo -a * If: %count
  %count = 0
  if 1 == 1 { inc %count }
  elseif 1 == 1 { inc %count }
  elseif 1 == 1 { inc %count }
  elseif 1 == 1 { inc %count }
  elseif 1 == 1 { inc %count }
  elseif 1 == 1 { inc %count }
  echo -a * ElseIf: %count
}

/elseif.test

* If: 5
* ElseIf: 1

They are not at all the same thing. In the IF section, each IF is evaluated every single time, incrementing %count every time. In the ElseIf section, since the first IF condition is true, the 1 inc %count command is executed and then control drops out of the if-elseif-else control structure.