Although they may have many children they are required to stay with only one spouse unless he or she dies. Amish also do not banish their children but some do choose to leave and are then are not able to contact anyone that is still Amish since they are "shunned". I have lived near the Amish and have always found them to be pleasant and nice. Often having a great sense of humor!!!!
The FLDS is way more extreme than the Amish. The FLDS is essentially a cult controlled by a few people. The Amish at least allow their people to go out into the world and decide if they want to be a part of the Amish community or not. The FDLS does not do this.
Even though the Amish have their own kind of lifestyle the flds are definatly more extreme. The Amish are kind and have respect for people. The flds treat women like theyre property and are extremly racist. The Amish have their kids got to school up to the 8th grade. The flds dont educate their kids resulting in entire communities not being about to read or write.
Both the FLDS and the Amish attempt to keep their people in cultures that separate them from the outside world. Some LDS people believe that having more than one wife is okay. Also, some very extreme sects exist within the FLDS church. Neither culture believes in alcohol, smoking, or other addictive behaviors.