I'd say rather than chosen, take Havocs with the same load out, they are a little bit cheaper I believe and have no downsides to it really, plus it'll be a little different than most lists
Also as far as the competitive side goes, spawn and bikes are the way, but if you don't fancy them, you could always try Maulerfiends, they can be nasty and are always fun.
Obliterators are really good, although expensive and work best in pairs with Mark of Nurgle, Mutilators are seriously avoided, and with good reason, they're just to immobile to do anything and that's not funny even in a friendly game :(
The Raptors are cool, though maybe take 10 if you really want to use them, they do tend to drop like flies sadly, although Mark of Khorne, a Khornate Lord with a jump pack and the Axe of Blind Fury is just nasty, not as nasty as a Juggerlord, but still... Nasty...
Other than that I'd say if you like any patron God, go for the ones you like, so if you're a fan of Nurgle (whoop woop), get Plague Marines, Tzeentch for Thousand Sons (very unappreciated), Dubstep Marines for Slaanesh and Khorne Berserkers if you fancy an assaulty army. Defilers are cool too, a very fun and unnapreciated unit by some.
So to wrap up, it's always good to consider your options with the Chaos Marines, they have lots of cool units, and can be fun but they are just not meant for competitive play really. I'd say make sure to take some Marks of Chaos, they can be extremely helpful and can make
CSM a very nasty army. Also consider what you want to play, undivided or dedicated to one God? Up to you but the best seems to be Nurgle.