whoops i think i just said up there that a 999cc mpi was likely to be 16v... duhhh
mind you theres always that brazilian 16v thousand cc that kicks out more than a G40 when you turbo it - good lord.
(if we talk purely 4cyl for the moment, or you can substitute "SOHC" and "DOHC", whatever)
8v's are good all-rounder everyday engines, nice low down torque but tend to have the power fall off quite a lot at the top end - e.g. mine peaks at 5200 with peak torque about 2800, many others do it about 5000, there's even a few about that have their peak power around 4750 - 4900 and torque about 2500... and that's in a petrol burner! Grunty as anything though and great to trot round town in, just get their asses whipped much past 70mph.
Can use clever tricks however to make them more sporty as there's a lot of untapped potential. GT is a good example... take a regular 1300 8v, give it multipoint injection, give a minor tweak a few other things, suddenly you've got +20hp with the torque holding strong to a good couple thou revs higher... and lots left to give a hardcore modder.
16v's tend to be more performance oriented from the factory, indeed might not be so great at the bottom end of the revs or cruising round the city (well, can be - depends on the setup*) but the freer flow of gases in and out of the cylinder means that the engine can throw out the same strong midrange torque and hold it into the higher revs, producing much more power and allowing lower gearing too. Will whup a similar cc, similar tuned 8v once you're up to A-road speeds, and leave it for dust on the motorway. Power peak tends to be 6000 or more and torque almost exclusively 4000 and higher. Can get crazy power figures out of small cars with the right setup (hence the japanese using it a lot

)
* just as you can have cammed, ported, etc 8 valves like a traditional hotrod (or indeed a modded G40!) that have a lot of high end power and are lumpy at the bottom, there's enough valvers about with very good all round competence..