First of all, I(we) need a clarification, LionChief or LionChief+ (plus)? If I understand a reply made by Gun Runner John (GRJ), LC+ require a DC motor that has timing marks on the flywheel so that a constant speed can be maintained. Motors in trucks do not allow this due to space constraints. Therefore, I'd guess that LC+ are vertical DC motors only w/r/t diesels. LionChief, to my knowledge, does not have the constant speed feature and therefore motors can be located on the trucks or in a vertical position.
Further, I've had both type of truck motor setups with diesels- i.e. single truck powered, both trucks powered. When Lionel first did this, I was a little reluctant because of change. (Change is bad - that's a work joke . . . anyway . . .) The single truck mounted motors were placed inexpensive starter sets and lacked power when a long string of cars was placed behind them. I would often add a second powered truck for better pulling power. Other then that, I had/have no issues with them.
I'm not an expert on this subject, so hopefully others who are more knowledgeable will reply.
Steve