best yeshivas

The two best yeshivas that I ever saw were both in NY. Though I saw lots of yeshivas in Israel and in many other places around the world I was most impressed with the Mir in NY and Shar Yashuv in Far Rockaway. The reason is these places were the closest thing I saw to learning and keeping Torah for its own sake. It was not just that they were both very much into learning "Beiyun"(--in depth) but also there was a spirit of "Torah for its own sake" that I never saw elsewhere.

[I have tried to express in a few essays what is unique and special about authentic Torah but nothing really gives the power and impact of learning in one of these two places.]
[The main thing about the yeshiva world is to learn and keep Torah. Since most people are far from NY, the best thing is to get your basic set of the Oral and Written Law, and just plow through them. The actual world of yeshivas itself tends to be very confusing because of the numerous cross currents. For those like me that simply do not want to know or hear about that it is best just to make your own spot a place of authentic Torah (מקום תורה) and do not be concerned what others are doing.] It might be a good idea to do research and to write  a paper on the yeshivas, and the yeshiva movement as it started with Reb Chaim of Voloshin. But the short and sweet of it is simple. There are places which are more or less devoted towards learning and keeping straight Torah. Some are better and some are worse but as long as straight Torah is their focus they are basically good. The trouble is the cults that pretend to be keeping straight Torah and they are very dangerous and ought to be shot on first sight.

What is straight Torah? The basic Oral Law is the two Talmuds. The basic set of Halacha is the Rishonim Rif Rosh Tur Shulchan Aruch of Rabbainu Joseph Karo. The best of the later achronim are the Pnei Yehoshua, R Akiva Eiger, and Reb Chaim Soloveitchik, and Rav Shach's Avi Ezri.

Great tzadikim   such as the Gra and Rav Shach  became more and more aware of the danger of counterfeit movements entering in and ruining genuine Torah as time went by, and they wrote specific warnings  about this. Other people have chosen to ignore the problem and thus indirectly caused many to fall. 
The cults teach and practice and try to bring people to their imitation Torah and succeed because no one of real stature combats the problem. False teachers was a problem addressed by Reb Nachman himself;- and though the movement founded on him is full of false teachers, still there is great importance in his lessons, -and this one among them. Fake Torah is much worse than no Torah.

One way the cults trick people is by camouflaging the belief being taught and until the subject is willing to accept it.

They claim to teach Torah. But think for a minute.

 Imagine a man with a bottle in his hand. There is a colored liquid in the bottle and there are many healthy ingredients in that bottle. There's water in it and and  excellent ingredients. But there happens to be an amount of prussic acid, and though it's a very small amount it can kill anybody who drinks out of that bottle! What's the point of praising the good ingredients when there is rank, lethal poison in the bottle?" The pseudo Torah cults add Torah to their poison to hide what they are actually offering. [The Sitra Achra, the Dark Side, imitates the realm of holiness but one with his eyes open can tell the vast difference.]

The major reason the Gra signed the excommunication was for this very reason. He saw the attempt to subvert the Torah. The main objective of cults is to break up your relationship with your parents and wife an children. They are scum pretending to be superior beings.