I agree, Both are true... when designing a wing use pressure, as a pilot figuring out how airplanes work, how different aerodynamic surfaces interact, and so on, physical lift is better. Upwash is the enemy, it is moving air the wrong way to create lift... the only reason the increase in downwash created by the wingtip vortex doesn't increase lift is because an equal amount of upwash cancels it out. In fact that effectively increases the angle of attack and increases the drag. But the effects from tip vortex are superimposed over the downwash that exists in 2D flow... in other words there is always more downwash then upwash... Here is a good website on the subject http://airsports.fai.org/feb99/feb9904.html

Ty