Putting presentation logic in controller is a good practice in Ruby?

Some recommendation [1] suggest you to use

<%= current_user.welcome_message %>

instead of

<% if current_user.admin? %>
  <%= current_user.admin_welcome_message %>
<% else %>
  <%= current_user.user_welcome_message %>
<% end %>

But the problem is you must have the decision logic somewhere in your code.

My understanding is putting the decision in template is better than controller as it make your controller more clean. Is it correct?

Are there better way to handle this?

http://robots.thoughtbot.com/post/27572137956/tell-dont-ask

In my opinion, if the text is the only thing that changes, it doesn't belong in a view. If you needed to restructure the page, that's presentation logic. This, this is just data being different.