I like to use a preamp which has a little bit of character when driven, like a valve preamp, or using a transistor preamp with a valve microphone. The reason I do this is because it makes a relatively soft microphone sound a bit like a 416.
I also think it is a bit too difficult for me to work with a shotgun microphone like the 416 in an ADR situation, where I cannot actively control the position of the microphone (unless I can afford a boom operator for the ADR - which never happens on my films). So I use a cardiod microphone like the MKH-50 in order to have a decent pickup pattern. The only exception is when I work in a very large ADR studio, where I can get the mic more than a meter away from the actor.
The most precious part of dialogue is life, the little errors, the sense of movement. I think you lose that when forcing the actors to stand too still. You need these "errors" if you want the ADR dialogue to match the production sound. It is a lot easier to make the ADR work in the mix by matching up different types of microphones, than it is to make a stiff ADR acting performance work with a vivid on set performance.
When matching up the ADR to the production sound, I use speakerphone quite a lot. Especially the mic modelling, where you can degrade the microphone. I also use altiverb. I usually make a copy of the sound on another track and audiosuite the copy, in order to get a mono version with a credible reverb, because I need quite a lot of reverb to match the natural reverb of the production sound.
I can then mix the clean and the processed track until it sounds close to the production sound. I also EQ the ADR dialogue until it matches the production sound.
I send all of the dialogue, ADR and production sound, to a reverb (at least stereo, sometimes 5.1) which ties it all together (like Lebovski's rug).