Will come down to the individual car and driver. Both are very close power wise (and underrated at that), but there tends to be alot of variability between individual LS1s. The Firehawk does have "ram-air". The hood is NOT a Raptor hood. Its an SLP hood specific to the Hawk, more subdued than the WS6 hood, and also has heat extractors above the heads. IMHO a cleaner looking setup than the WS6, but then again I own a Hawk, so I may be a little biased ;-) Check out
www.firehawk.net for lots of Hawk info.
Top speed will be the same, as they are speed limited to 160 (have heard they are still pulling when the limiter kicks in). Note that the limiter depends on the tire option from the factory, but all WS6s and Hawks have z-rated tires so will have the same limiter.