I have no way to know which company's practice problems are the closest to the real MCAT since I have only used TBR and EK. I also doubt that most people who vote can fairly compare the companies unless they spent a fortune on MCAT prep.
I can say that the TBR physics, orgo, and gen chem problems were tougher than those I was given on the real MCAT, so if you want a prep that makes you stronger than you need to be, TBR is a great option.
EK's 1001 problems for physics were generally of similar difficulty to those I encountered on the MCAT. Their orgo problems were less difficult. I did not buy their gen chem 1001 book, so I cannot speak to its difficulty.
I did not do practice passages for biology except for those on practice exams, so I cannot speak to any company's level of difficulty there.
EK's verbal 101 book was pretty similar to the difficulty of the problems I saw on the real MCAT.