Why is there 2 options of Meta tags?

[Subash]

Very good question

yes blogger has given in built meta tag option.but i prefer giving custom meta tags in the template

but you can do one important thing with the inbuilt metatag option that is just enable and give ur brand name as title and description if u want

with that if you insert a code in ur blog template you will have a nice title for all your blog posts
like
"your post title | brand name" which is very usefull tip for increasing traffic for all your blog posts and quick index in search results

insert this code inside your head tag
code
-------------------------------
<b:include data='blog' name='all-head-content'/>
<b:if cond='data:blog.pageType == "item"'>
<title><data:blog.pageName/> | your inbuilt meta tag entered titile </title>
<b:else/>
<title>
your title entered in the template
</title>
-------------------------------

Hope my post helps your blog to increase traffic