The VVT and V-TEC in operation in the real world
The Toyota engines seem to run slightly more aggressive cams than the Honda's, and so at lower revs they seem to (anecdotal evidence here ...) be a bit more pleasant to drive and make a little more power. There's also less of a transition when the cam shifting systems operate, but this is obvious due to the Honda system swapping over to a much more 'racy' cam profile. I think that the Honda's may seem to be a little 'flat' at lower revs because of this relatively large contrast, but I'd have to drive one and see a dyno chart to make verify this.
Pro's - Both systems allow you to have an engine that's quite a lot more powerful and yet still driveable than a 'conventional' engine would otherwise possibly be. The V-TEC is the obvious choice for outright power, and the Honda's certainly seem to rev a heck of a lot more than the Toyota's do. (The S2000 red lines at a stratospheric 9,000rpm - stock!)
Con's - You are pretty much stuck with limited modifications to the engine, eg, air filters, extractors, etc, to get more power. The reason for this is the very system that give the engine all that extra power - The cams & VVT/V-TEC. You can of course use larger cams to get more power, but this defeats the purpose of having the VVT/V-TEC in the first place. You'll most likely lose power at low revs, and not gain a great deal at high revs. (The VVT will gain proportionally more than the V-TEC, however, as the V-TEC head is optimised - well, compromised - for the 'big' cam & 'small' cam and so using a larger cam may not help much at all)
So, if you want an engine with power like a racing engine, then you're better off building a straight race engine right from the start. Or maybe a turbo engine ...
The other concern I have is the longevity of these sorts of engines. I believe that the VVT system would be largely trouble free for the life of the engine provided that you keep the oil clean and change it regularly. Even more so with the V-TEC, as with all it's little bits & pieces in close formation in the head I'd hate to think what would happen if some of those little locking pins didn't engage properly at 6000rpm+. All that being said though, I have it on reliable advice that Honda have never had a warrantee claim for any V-TEC engine in the area of the head and/or valve gear. Quite impressive.
I think that perhaps the best long term solution to getting large amounts of power from a relatively small engine is still by using a turbo, but if you like to hear the engine scream at high revs then one of these two systems is the way to go.