Bug's, T-Fex Vs Carni

So the question i am wondering is....TyranoFex or CarniFex for Tyranid Heavy Support/Heavy Tank busting?  I would bring 1 Trygon already, but would rather not spam them even though i think they're pretty awesome for the points.  Mawlocs don't impress me much, Old one eye is poop, and Biovore's are good but probably not something i want for lots of little reasons.  So two HS slots are open......

First we'll start with the Carni:

Pro's

1. Modest starting point cost, for a Monstrous Creature anyway.
2. Strength 9 makes him the best unit in the codex for Melee Tank busting
3. Living Ram makes it possible for the Carni to attack against Powerfists ect. first if it gets the charge.
4. The ranged options for the Carni are numerous and mostly good, some are considered better then others like the "DakkaFex" which includes 2 sets of Twinlinked Devourers.
5. When taking a good ranged weapon, you have a Versatile unit capable of melee and ranged support.

Con's

1. 4 Wounds honestly feels low to me, the Carni is supposed to be the original living tank i think 1 more or at least the option to purchase 1 more should be present.  That or perhaps a Toughness of 7, the point is the Carni is easy for many armies to put down in a single turn if it's caught out of cover, i should know....i'v done it many times =)
2. 4 Attacks also feels low when combined with a low weapon skill.  The Crushing Claw upgrade needs to be a guaranteed number of attacks or a larger amount for it to be worth it's hefty point cost and detriment to your Initiative(i mean it essentially removes the Carni's one Unique special rule).  The Carni really needs to keep Scything Talons to be effective in melee at it's point cost, without them its basically a Chainfist Terminator.
3. No Inv Save, sure its basically a con of 90% of the nids....but at this point cost it's a big Con.
4. Ranged Weapon options while good, weaken Melee ability, and force the Carni to walk slowly each turn without a Tervigon's assistance.  It's the common case of utility vs excellence, you can make him good at it all but it removes his ability to be amazing at either.
5. Initiative 1 means Space Wolf players will be trying to get you to fall down a crack, all rune priests are priority 1 for death.

Some builds i would consider:

"DakkaFex"

2x Twin-Linked Devourers with brainleech worms

Adrenal Glands

Clocking in at a straight 200 points, this Carni is a mid range support unit thats decent in melee but pretty fantastic on lightly armored infantry or light vehicles.  The adrenal glands let it strike with Space Marines on the charge, and give it str 10 against vehicles and units of Toughness 5 models that i would rather instant death.  The problem here is melee support, your getting 4-5 attacks on WS 3, that means you should miss 2, leaving you with 2 hits.  While individuals and the aforementioned Toughness 5's will be scared of him, units of models need not fear as he just doesn't have the attacks to win combat against most foes.  

"Screamer Killer"

2x Scything Talons

Adrenal Glands

Frag Spines

Bio-Plasma

At 195 points he's a tad cheaper, and is clearly better at melee.  The Scything Talons give you a much better chance to put out the attacks in the to hit roll and his str 9/10 makes sure they hurt once they hit.  Frag Spines lets you assault anyone you want, and adrenal glands again puts you on par with marines and into instant death range for toughness 5.  Bio-plasma is the oddity here, in one corner it adds versatility to the Carni allowing him a useful shooting attack with a low AP, something most nid weapons lack.  However, its also short range and is mounted on something that really wants to close distance first and assault asap to earn its keep.  If the plasma had something special that made it scatter less or made it ordnance so it was more reliable then i would be happy, but atm i'm not sure its worth its points for short ranged plasma cannon that lets me keep my CC weapons.  Removing Bio-Plasma however makes him the cheapest option.

"Cannoneer"

Scything Talons

Heavy Venom Cannon

Adrenal Glands

at 195 points this Carni is tooled to be the Versatile slow moving unit, it's HVC allows it to provide much needed long range Str 9 blasts to the front, opening up vehicles for others to attack whatever s within, and it keeps a single set of Scything talons so that it's a bit more dependable in Melee.  It's problem then stems from being not all that good at either ranged or melee, and having a gun to shoot means its gonna be walking each turn so it wont be assaulting anything quickly unless its foolish enough to come to the Carni.

So on to the TyranoFex option:

Pro's

1. Best Ranged Anti-Tank in the Codex, hell its great anti-tank by anyone's terms.
2. 6 Wounds, i guess it's in the "bigger MC" category, with 50% more wounds then a Carni it's survivable and will likely never die in a single turn.
3. it's save of 2+ is Amazing, especially when combined with the 6 wounds....it really will survive unless focus fired, and again even then your hard pressed to bring it down in one turn.
4. No official model means it's up to you, we know its big based on the stat line so use that to make a large LOS blocking cover granting beasty for your others to hide behind, with the above mentioned survivable traits he works well here.
5. Guns guns and more guns, sure the Rupture cannon is the highlight here, but packing the ability to fire it, a str 5 large blast, and a poison 2+ template all in one turn and this guy can bring serious serious pain to anyone that gets close.
6. Regeneration while the most expensive on this unit might actually be worth the points here.....

Con's

1. Expensive as can be in the codex, this unit isn't something your likely to see spammed...then again Land Raiders are spammed so who knows.
2. Like the Tervigon and Mawloc, it's not great by Tyranid MC standards in melee. WS 3 and only 3 attacks mean its not gonna clear units out on it own.  It's not terrible overall but devoted assault units may be something you try to avoid or at least don't send it into assault un supported.
3. BS 3 means you will average a single hit with the rupture cannon each time you fire, i actually don't have a big problem with this as you have a 75% chance to get a single hit, a 12.5% chance to miss entirely, and a 12.5% chance to hit twice.  I call that dependable, with burst/fail potential, unfortunaly your bringing this unit to shoot and those odds while fine are not fine when the point cost is considered.
4. The weapons carried are not a good combination when you take the Rupture cannon, the cannon is super ranged while the other weapons are all short range...chances are you wont be firing the short ranged weapons until late game, which means their point cost is most likely a waste overall.  If it could maybe choose two targets to shoot at this would fix the issue, making the short ranged weapons at least capable of defending the T-Fex from pesky fast attack units ect.
5. Imitative 1 like before, but worse here because this is more points going down a crack.....
6. Again no Inv save, not as much of an issue for the T-fex as its got basically everything else going for it survival wise but still a con none the less.

The only build i really consider here is below, Regeneration would be nice on this unit but it pains me to sink those points into the unit with it's already huge price tag of 265....i am guessing my opponent s will ignore it mostly and its armor save and stat line will see it through most battles.  No need to explain the build, as its explanation is rooted in the pro/con above.

"Tanka"TyranoFex

Rupture Cannon

Desccator larvae

Cluster Spines

Thoughts on the two units, experiences with them, builds i haven't considered and why?