First of all,
bloginfo will output value ;) If you want to get the value, you should use
get_bloginfo takes one param from predefined set (You can find all possible values here: http://codex.wordpress.org/Function_Reference/bloginfo). Only part of these values are values of options (in such case
bloginfo returns value of that option).
Returns information about your site which can then be used elsewhere
in your PHP code. This function, as well as bloginfo(), can also be
used to display your site information anywhere within a template file.
On the other hand,
get_option can be used to retrieve value of any option stored in options table.
A safe way of getting values for a named option from the options
database table. If the desired option does not exist, or no value is
associated with it, FALSE will be returned.