Comparing to a text value can have problems if users decide to later change that text - which is easy to do in Magento for attribute sets. One other option is to use the underlying id instead which is never going to change.
You can get this by looking up the value of the attribute_set_id column in the database using
select * from eav_attribute_set;
This number is also in the edit link in admin which is in bold below
http://.../index.php/admin/catalog_product_set/edit/id/10/key/6fe89fe2221cf2f80b82ac2ae457909ce04c92c51716b3e474ecad672a2ae2f3/
Your code would then simply use that property of the product. Base on the id of 10 in the link above this would just be
if (10 == $_product->getAttributeSetId()) {
//Do work
}