The catch he dropped wasn't a simle easy one, the ball really took off Kulasekara's bat who was swinging hard and he slashed at it, and it just got to Wade quicker than he thought it would. Only mistake he has made so far.
My view is that there is no point in keeping an older bloke in Haddin in the team if he is going to drop catches and not scores runs, then they may as well give the job to a younger keeper (Wade the front runner obviously) and try and groom them for the back to back ashes series coming up.
Wade's First Class keeping record is better than Paine's, with 50 more dismissals in the same amount of games (50 games to Wade, 46 to Paine). Also, Wade is 3 years younger than Paine, and doesn't have a history of injury problems, which is why Wade has already played a few more games then Paine has, despite being 3 years younger.
Another thing is Wade's favour is that his batting record is better than Paine's. Has scored more runs and in less innings - Wade 2490 in 74 innings compared to Paine 2467 in 84, and his average is almost 10 better - Wade 40.16 compared to Paine 31.62
To me, it is easier to make big improvements on the keeping side, then it is to make those big improvements on the batting side. Just look at Prior, he was criticized for being batsmen who could keep, but he really worked on his keeping and now he would be the best keeper/batsmen in the world. I didn't see Prior when he was struggling, but to me, Wade isn't bad at all.