Sorry, but wake vortices are not reduced. They are different. With the winglets there are the two components, the small core and the large core, virtually 2 separate vortex, and they act much differently.
The small core are very high velocity, and a smaller core, which may break up earlier. The large core are slower moving, and tend to last longer.
Under the right conditions, a small core will transform into a large core. This tend to happen when the air is drier, and calmer. Under this scenario, the vortex is much longer lasting, and therefore a much higher chance of WVE.
The flaps on the ac have the largest effect on wake vortex. A 737-800 on final with flaps 20, generates a much different vortex than the same aircraft with flaps 30 and/or 40. The same aircraft.
IF you want to see some real interesting vortices, look at the A380 on final....