Didn't Rommel have the largest concentration of Panzers / Panzer Divisions since Kursk?
Not sure. There were a lot of paper-divisions around, just like many of the battered eastern-front units were sent to the west. Wikipedia says 2200 tanks from june-august. same number lost. Allied losses says 4000 tanks. Kursk has 40% more tanks on a period of 10 days. Not really sure how to read it.
Compared to what was going on elsewhere it was a sideshow. And while Rommel techincally was in charge of a large force, much of it (the reserve) was out of his control entirely, whereas Monty could command all the troops that could be provided shipping for.
and I think that Overlord exemplifies how good some of the allied Generals were; Marshall/Alanbrooke were willing to let their staff control the operational detail, Eisenhower was willing to let Monty command in the field and Monty was willing to let Patton be the one to drive out in operation Cobra. At all levels you have officers who not only know their strengths but also trust their subordinates to perform better than they; a leader's greatest quality is to know when someone is better than he.
I think you overestimate the mutual trust in this chain of command. Overlord, indeed the western allies' operations were dominated by what could be accomplished diplomatically i.e. what compromises could be reached, rather than who trusted whom and how able this or that commander was thought to be by his peers. A good glimpse into this relationship is Alanbrookes diaries, and it wasn't limited to inter-allied relations but also largely between the different branches and indeed within each branch. (If you haven't already, the diaries are worth a read).
With the German's we see a structure where each commander doesn't trust his subordinates and tries to control everything himself. Rommel's desire to 'lead from the front' is just another way of him not trusting his subordinates to do their job!
Perhaps at the general-rank level. German doctrine was very much built upon unit independence, where the officer in charge thought up solutions to orders himself, and carried them out. Once you reach a certain level of rank (i.e. army- or theatre commanders) I'm sure there was immense rivalry and suspicions. That Rommel didn't trust his commanders is disputable. I think he simply preferred to be in the thick of it (probably to compensate from his lack of a staff education). But it's no secret he was clashing with his immediate subordinates on a regular basis - and even more so with his superiours (various Italian generals and Kesselring especially).
But I'm not sure you can apply it broadly across the Wehrmacht. If your example with Rommel is to hold water, it would mean that all generals not leading from the front did indeed trust their subordinates - something that we know is not true (Manstein is a famous example (i.e. the Kerch peninsula "incident" (Sponeck)).
Plus, there's plenty of evidence that show allied generals being highly suspicious or critical of their subordinates/superiours/peers (especially across nationality).
Also, I like your comment about Alanbrooke, but I think that the successes of Roosevelt, Marshall, Churchill and Alanbrook was determined by the dynamic of their skills and personalities; that is they complimented each other.
I know little of Marshall's personality or capability. I know Roosevelt liked him a lot and I know Alanbrooke was unimpressed (which he also was of Eisenhower - but being surpassed by him re. Overlord, he had a vested interest). There is little doubt that especially Churchill managed to pick his men better that his immediate and comparable enemy, Hitler, and managed to listen to their advise (something Hitler seemed adverse to!).
Roosevelt managed to pick wisely, but I wonder if so many others couldn't have done just as well as Eisenhower/Marshall. US capability came in form of force, numbers and ressources - something that would have been applied by any and all. UK and Germany were more limited in their capabilities and couldn't afford strategic blunders, so the difference came down to the individual.
But I suppose your claim of German generals being suspicious could be traced to the organizational dispositions of, ultimately Hitler alone, but by proxy especially Himmler and Göring, when building their own little (big!) armies, combined with Hitlers irratic behaviour towards generals. After Brauchitsch it seemingly became "every man for himself" (maybe even sooner). Churchill managed to pick the right man (at least in the second try) and stick with him. Same goes for Roosevelt and Stalin. I guess continuety, like quantity, has a quality all of its own.