Sorry, I cannot really decide which one of the 2 is the best. I use 2 quite a lot in my routines, as they both can be used for completely different reasons.
I use a svengali myself not as a standalone effect, but more as a utility. I think its a great way for the spectator to force a card on themselves. Although I must admit I often have a svengali in my jacket pocket, as if someone asks to see a trick, I am ready at any time. And as people have said on here before, although the method is starting to get better known, its the way you can present it. The only thing I never do with a svengali now, is to show all cards the same! I know its a very strong visual effect, but it really draws a big full stop to that decks use. Fine if it is your last effect, but IMHO it gives away too much to the spec.
The ID, on the other hand I carry as a complete Insurance policy. In my routines I do quite a lot of haunted pack effects. Mostly Gimmicked ( I will leave the explanation at that !

) and some ungimicked (Derren Browns "Devils Picture Book" brilliant!) However if the gimmicked ones dont work for any reason

( I am sure people know what I mean! ) The ID can always be used as a great out.
Sorry. Dont know if this helps or not!
