There is no stronger card trick than the svengali deck PROVIDING you show the cards to be all different and then all the same again! The people freak out when you do that!
I completely disagree!! And I am even talking about using the sengali deck correctly!!
First you show all cards are different. This can even be done by springing the cards from one hand to the other. When the cards are shown to be the same, it can be done extremely convincing by springing them accross the table so they fall down all face up accross the table with all cards being the same card. (the opposite display is possible with a "reversed" svengali deck).
From what you write it is not clear that this is how you perform the display with the svengali deck. It is NOT how beginners usually do it, however let us first clarify what we talk about. The springing display is in my view the correct handeling and is endeed quite magical.
However to suggest this is the strogest you can do with a deck of cards is simply NOT correct. It will often get a strong reaction, but strongest reaction is not always the same as strongest magic.
In fact a "reverse" svengali deck where the cards can be sprung accross the table and all cards very convincingly are displayed as different can be the precursor for much more magical effects. One spectator might select a card randomly and the other spectator stop at a card etc. And all handeling happens in the hand of the spectators!!
There are many other effects that also are stronger than displaying the cards as different and then displaying them as the same, but I do not wish to discuss them here.
I understand Soren's concern and I can assure him that it is quite wrong. However he is not MARK LEWIS and I am so the fact that he has it wrong is perfectly understandable.
Well, then I am in good company!! I am pretty sure that Dai Vernon on his revalations videos discuss this issue together with Gary Quellet, Steve Freeman and Michael Ammar and they all share the view I have stated. As far as I recall they all take the view that its a mistake to display all cards as the same. I might be wrong on the source, however there are more that 20 hours of videos so I am sorry I cannot be more specific with the reference.
Max Maven is essentially using a svengali deck in some of his efffects on his Mentalism DVDs/Videos. If Max Maven shortly after having performed an effect with the "Mind's Eye Deck" (Max Maven Vol 1) continue the display some of this decks svengali properties, not only would he be ruining an excellent mind reading effect, but also have reduced the magical level of the performance.
Of course if performing for a bunch of half drunk spectators in the local pub, it might get a stronger reaction if all cards are shown to be the same, however Max Maven is Max Maven and Mark Lewis is Mark Levis.
To show all cards being the different and then showing that they are all the same is in my view NOT the primary use of a svengali deck. If however one decides to go down the (dubious) route of doing this, it is important to least take the time and learn to do it the "professional way" springing the cards accross the table.