To buy the 5.0 or the ? That is the question. True to the plethora-of-packages Mustang it's based on, the relative value of Ford's new 550 HP supercar-killer all depends on which option boxes you tick.

Full Disclosure: Ford wanted us to drive the mildly-upgraded GT500 so badly, they flew me all the way to the land of my ancestors, put me up in a trackside hotel and fed me a dry, taste-free pulled pork sandwich. Honestly Ford, this is like the tenth time you've fed me bad barbecue, what've you got against slow-roast pork?

For 2011, Ford's taken the , swapped its heavy iron block for a new aluminum one with a wet sump (The Ford GT's engine, on which the GT500's is based, used a dry sump, this is a different block despite the aluminum), in the process dropping 102 lbs from the nose and 120 lbs overall. Power is also up 10 HP to 550 HP and torque remains unchanged at 510 Lb-Ft. Electricity replaces hydraulics for the power steering and there's a new Z-brace for the steering rack that ties into to the radiator support, similar to the one employed on the . HID headlights are now standard.

With the 2010 Shelby GT500, SVT's engineers claim they've turned a 500 HP Mustang into a 540 HP…

That doesn't sound like a lot and it doesn't add up to a huge difference in the driving experience, but there was a huge amount of effort involved in making those changes and the numerical benefits they bring are pretty impressive. The GT500's cylinders ditch liners in favor of a crazy spray-on anti-friction coating called (this ditches 8.5 Lbs all by itself) and the new engine manages a gas-guzzler tax-free 15 MPG city/ 23 MPG highway EPA figure. The extra power is largely thanks to a new 2.75-inch exhaust system that also ups engine noise.

The 5.4-liter supercharged aluminum V-8 in the '11 Shelby GT500 is 100 pounds lighter than it…

Road noise has been reduced perceptibly, replaced with exhaust noise and the Electric Power Assist steering is noticeably sharper. You can't feel the power increase (which doesn't improve the 4.4 second 0-60 or 12.1 second 1/4 mile times). Ford flew me all the way to North Carolina, then made me drive to Virginia for this?

Luckily there's more. For 2011 there's a new, optional, $3,000 Performance Package that really makes the model update worthwhile. Check that box and you get near-slick Goodyear Eagle F1 Supercar G: 2 tires; wheels grown an inch to 19-inch (front) and 20-inch (rear) wheels while shedding weight; the rear axle ratio is increased from 3.55 to 3.73; ride height is lowered 11mm (front) and 8mm (rear); spring rates are up 20.5 percent (front) and 9.5 percent (rear) and damping is increased in kind. All that's enough to knock nine seconds off the GT500's lap time around the 4.1-mile Grand West course at Virginia International Raceway.

The Performance pack also utterly resolves the 5.0/GT500 dilemma. Where the standard GT500 delivers numbers that surpass the regular Mustang, the driving experience remains incredibly similar. You're only paying about a half second 0-to-60 penalty with the regular Mustang. Factor in the $18,000 premium for the Shelby and the 5.0 is a no-brainer. Tack on the Performance pack, however and things are equally black and white in the Shelby's favor.

It's amazing what a bunch of added grip, shorter gearing and increased suspension control can do to a car. Through VIR's fast, off-camber corners and over crests that had the 2010 GT500 wiggling around imprecisely, the Performance Pack-equipped '11 is now planted an confidence inspiring. Driving the two cars back to back, it was also surprising how laggardly the '10 felt in comparison, all due to its taller gearing; third gear was enough to pull the '11 out of corners that the '10 needed second gear for.

The tires are really the highlight of the package. Developed specifically for this fastest of Mustangs, the Goodyears noticeably improve turn in, raise mid-corner speeds and allow you to get more of the power down sooner. Sadly, they're only making them for the larger wheel sizes so sticking a pair on your 2010 model won't be terribly easy.

The other big change for 2011 is to the convertible. Last year, we said the because it retained the old 2008 model's kill-you handling, only upgrading the engine and looks. This year, the ‘vert gains all the 2011's chassis upgrades while boosting its lateral stiffness 12 percent for improved structural rigidity and less cowl shake. You can even get the Performance Package on the convertible. Thank you, Ford, for listening to us.

Early this morning, our first drive review told you how awesome the new 2010 Shelby GT500 is.…

So is it worth spending $18k more than the 2011 Ford Mustang GT just to get some on-paper performance improvements? Not really, but it is worth spending $21k more to get handling that is now equals the 550 HP supercharged V8's massive straight line performance. The Performance Package-equipped 2011 Shelby GT500 is no longer merely a rip-roaringly fast Mustang — it's a well-balanced rip-roaringly fast Mustang.