Inline vs inline-block

HTML

<div class="area">
<p class="inline">Inline element margin 3em</p>
<p class="inline-block">
Inline-Block with margin-left:auto
</p>
<p class="inline-block-3em">
Inline-Block with margin-left:3em
</p>
<p class="block-centered">
300px wide p block element centered by auto margin calculation
</p>
</div>

CSS

.area {
background-color:pink;
display:block-flow;
padding:1em;}

p {background-color:red; color:white;}
.inline{display:inline; margin-top:3em; margin-left:3em;}
.inline-block{display:inline-block; margin-top:0em; margin-left:auto;}
.inline-block-3em{display:inline-block; margin-top:0em; margin-left:3em; margin-top:0em;}
.block-centered {display:block; width:300px; margin:0 auto;}