Template php code for calling class within template

Hi all

I have just developed a wordpress plugin and it is all strutured within a class called isimpledesign_feeds_class() so everything works fine and i am calling a function out from the class using.

<?php $isimpledesign = new isimpledesign_feeds_class(); $isimpledesign->isimpledesign_feeds(); ?>

i was just wondering if their is a problem calling it like this because from previous plugins i have always used

<?php if (function_exists('isimpledesign_feeds')) { isimpledesign_feeds(); } ?>

to call a function in the theme files.

Just wondering if anyone has any suggestions???

Thanks