Simply because it has most of the features i need:

1) it allows searching by just simply typing a part of item name in search field

2) it allows custom sorting which allows you to create custom categories

3) it shows craftable items by difficulty which helps a lot in leveling

4) it shows what you can craft even from incomplete ingreditens

5) it buys a required ingredients from vendor automatically on press of a button

6) it allows making a queue of crafting - for example if you want to make Mithril Spurs it will queue stone to make appropriate ingredient and Spurs itself - and on key press it starts making everything needed

7) it takes into account what do you posses in your bags, banks and even at your alts 

8) and last - it tells anybody what ingredients are needed for crafting something by pasting description into whisper, guild, raid or whatever chat channel

Available here : http://ui.worldofwar.net/ui.php?id=2092