To use Deffy, or not to use deffy

I need an opinion, (preferrably from a chaos player) on a heavy support choice for my Chaos Space Marine army, i'm thinking of either a Defiler or a Forge Fiend/Mauler Fiend for heavy support.

OOOH, BTW got a chaos land raider a while ago, nurgle themed.And on a money saving note,there's this hobby store in my town that gives major discounts on warhammer and warhammer 40k stuff, and i get even more of a discount on things because i am a returning customer, and this is directed more to henry and reuben, they are the only people that know where granite falls is so henry whenever you come down south i will show you this place and you can save money, because of lower taxes and if you order something thaat is not in stock, you save about 30% on stuff, however you could not wait for it to get here so i could get it to you via internatinoal mail.

HaLP! ian!