I do like both to be honest, the shambling ones I like because it looks very well done in large packs of zombies. Also I do understand why people use the enhanced reflex ones, because they can use those traits to startle an audience effectively.
Personally, from a startup perspective, I'd be more inclined to go with a shambling type zombie, purely because keyframing the animation can be achieved fairly effectively with python scripts and then motions adjusted with bezier curves on an individual basis.
Doing more with less basically.
Also, stylistically I think the whole "tortoise and the hare" effect with fast protagonists and slow moving, shambling antagonists is quite amusing.
I'm an enormous fan of Simon Pegg as a writer. He wrote an incredible article in defense of zombies and convinced me a lot. (His article was actually about how the slow model of zombie is the only worthwhile kind.) And Edgar Wright is a brilliant director: Shaun of the Dead is a very scary movie at the same time as it's incredibly hilarious.
That said, I'd love to compare it to Night of the Living Dead. I'm just scared that it'll be a letdown.
I remember watching Night of the Living Dead several years ago with friend when we were both into cheesy old films. We were expecting something along the lines of The Giant Gilla Monster or Attack of the Killer Shrews and were surprised to find that it was actually a very good, very gripping movie. It's no surprise that it sparked the genera.
In modern times there is a biozombie trend, when they aren't really "undead" so much as a sick human (eg I am Legend, 28 days later etc). I am not sure if it co-incides, but these biozombies seem to have enhanced reflexes, strength and hearing and speed etc... (whereas the old school ones were slow, sad things).