First, waiver of class-action rights. This is a big deal because there's a cottage industry of enterprising lawyers who do find a couple main plaintiffs, generate a suit on behalf of a large class against a deep-pocketed defendant, and settle for something around a dollar per class member plus millions in legal fees.
Second is a limitation on discovery and subpoena rights for plaintiffs. In a traditional court setting, you may be allowed to force a company to turn over extensive communication records and other documents, corporate executives to testify or be deposed, and even burden non-party witnesses (eg, part suppliers).
In many jurisdictions, companies that wish to use binding arbitration have to pay the entirety of the significant fees to fund the arbitration system (and in a timely manner). It's still worthwhile for them to do so, even if they aren't tipping the scales of justice one micrometer. With the exact same outcome as a court case, the arbitration fees are fully worth it to avoid discovery, better protect executives from being forced to testify, dodge class-action fishing expeditions, etc.