He is a much more complete MMA fighter then Sonnen. Their styles are really nothing alike other then that they have a wrestling base. If that's how far your level of insight goes, then yeah, they are the same style.
Weidman is a high class wrestler with extremely good submission grappling skills to boot. He faced Andre Galvao at ADCC as a purple belt and gave Galvao everything he could handle. His striking skills are coming along quite impressively as well. He's just one of those special kind of guys.
As far as I can tell, their styles differ in a few ways.
Weidman is more tentative and willing to stay on his feet to set up his takedowns. He's patient and calculating in doing so.
When he finishes a takedown, he doesn't sit in guard, but passed and lands shots to open up his opponent to look for submissions.
Overall, he's much more patient than Sonnen, and that, in my opinion, would be his downfall against Silva. Sonnen's success was in large part due to his aggression. He came straight at Silva and kept moving forward until the fight was on the ground. From there, he was able to hold Silva down and land shots at will. He was constantly fighting.
We've all seen what happens to patient fighters fighting Anderson. They start out being patient, and waiting for an opportunity. They eat a few shots, and it is no longer patience. They get stuck being timid, and become target practice.
People say Silva fans are scared of a potential Weidman fight. Not me. I'm a huge Silva fan. I want to see the fight.
However, the fight has a downside. When [if] Anderson beats Weidman as I suspect he would, all these Weidman "fans" would show their true colors as plain ol' Anderson haters. They would try to say that Weidman was never that good, and Anderson is ducking real competition.
I know how it works around here. I'm not stupid. But as an Anderson fan, I personally welcome the fight.