From what I understand from here, the myth that Hitler's bad choice to stop short at Dunkirk saved the British is false, and the Germans decided not to attack because their logistical support wasn't able to keep up. But Guderian wanted to strike, and I've heard from another source that he was bad at logistics compared to Manstein. Is it true?
EDIT: For the record, the answer turned out to be NO, as expected.
I think it's hard to argue that Guderian was inept at logistics. His interwar writings on armored tactics suggest at least a general understanding of how modern (for 1930s-40s) logistics worked and the logistical tail an armored division might require. Moreover, most of the time it's going to be silly to ascribe a logistical failure to a single officer, since logistics is even more than most military endeavors a "team sport." The other ingredient of logistical success is good predictions, for example, in order to know the ideal allocations of gasoline vs ammunition to send forward, you need to be able to anticipate the level of fighting vs. pursuit and exploitation a unit will end up doing. This means that hindsight is particularly unhelpful in analyzing an officers performance on a logistical level.
Having said all that in defense of Guderian, I'll note briefly that Manstein had a few years more staff experience, including as a supply officer, in the first world war. It's fair to say that Manstein was at least the more experienced officer in this area.
I take issue with the general meme that states that the Wehrmacht were not good at logistics.
Really, I see a lot of evidence to the contrary. The panzer drives that took place in the Battle of France and the early stages of Barbarossa were extraordinary undertakings, involving the movement of vast numbers of men and material over vast expanses of hostile territory with little in the way of logistical crises.
Furthermore, the aerial re-supply of the Demyansk and Kholm pockets was by no measure a mean feat of logistics.
It is true that the Germans had chronic problems with poor intelligence and incoherent strategy, which of course greatly complicates any logistical undertaking - its hard to pack for a holiday when you don't know where you are going, when you are going, for how long you are going to be there, or what the locals are like!
In the specific case of Dunkirk, we have to bear in mind that the panzer divisions had enjoyed a degree of success so rapid and complete that it exceeded everyone's respective nightmares and dreams.
And yet the logistics, for the most part, kept up.
The halt order wasn't given because of a shortage of food, fuel or ammunition, it was given because:
The panzers had outrun their own un-motorised infantry and artillery formations meaning that there was a severe danger that they could be cut off and isolated by a well-organised counter attack. This was emphasised by the battle of Arras where an ad hoc British battle group did an awful lot of damage to 7th Panzer.
The tanks involved had fought their way a considerable distance across enemy territory. Tanks, especially 1940's tanks, aren't like modern cars that can be driven for hundreds of miles without any maintenance. They break down constantly and demand hours of routine maintenance every day. This takes its toll - regardless of the nature of the Panzer casualties, the fact is that Hoth had lost a third of his tanks and Panzer Group Kleist's was at 50%. The tanks badly needed a break for repairs and refitting.
German intelligence reports specifically highlighted the fact that the ground in the area around Dunkirk was unsuitable for tanks. If it had rained, the panzers would have bogged and bellied in the Flanders mud.
Hitler himself stated in September 1939 that "under no circumstances must tanks be permitted to become entangled in the endless rows of houses in Belgian towns". This is underlined by the fact that tanks operating in built up areas can expect to sustain enormous casualties even against a poorly equipped enemy - 4th Panzer had lost 57 of their 120 tanks in fighting the streets of Warsaw the previous year.
Most of France was unconquered and a good portion of the French army was undefeated, plus no one, not even the British Admiralty, envisaged that the evacuation would be so successful. Its not referred to as a miracle for nothing.
Now, Considering all of the above, why risk throwing away your precious armour to defeat an already defeated enemy?
The stop order was simply sound military sense, and without the benefit of hindsight, to have done otherwise would have been ludicrously reckless.