I might be mistaken, but the difference is not only semantically, but in behaviour as well.
With @push you append as many times as needed to a stack, while (by default) you may fill @section only once in your views.
In some situations this comes in handy when you need to add content from different locations across your template files or in loops:
index.blade.php:
@extends('master')
...
@for ($i = 0; $i < 3; $i++)
@push('test-push')
<script type="text/javascript">
// Push {{ $i }}
</script>
@endpush
@section('test-section')
<script type="text/javascript">
// Section {{ $i }}
</script>
@endsection
@endfor
master.blade.php
@stack('test-push')
@yield('test-section')
</body>
result:
<script type="text/javascript">
// Push 0
</script>
<script type="text/javascript">
// Push 1
</script>
<script type="text/javascript">
// Push 2
</script>
<script type="text/javascript">
// Section 0
</script>
</body>