Assuming that the contract specifies the forum, you'd want to look into how 'fair' the past decisions for matters relating to whatever it is you'll be doing have been.
You'll also want to get a sense of what the forum's arbitrator pool is like, i.e. who are the arbs and how qualified are they to actually sit on a panel.
Additionally, look for language that specifies where hearings must take place, and/or forum rules/policies on specifying hearing locations (or actually how the process works in general). The last italicized bit is quite important because contracts can say just about anything, but fora often have rules that can void contract language that is deemed unfair, unethical, etc.
Other considerations: up-front and long run costs, turnaround times, ability to receive explained decision and to appeal decisions, ability to forum to enforce decisions/judgements... Probably forgetting some things, but those are the major ones. Oh, yeah, precedent. At my forum, past panel decisions had zero bearing on other cases. I mean that literally.
Possible reason not to opt out: you might fair worse trying to go to court, based on costs, turnaround time, precedent, or some other factor. Also, your company may view you as a troublemaker if the typical behavior is simply to sign the agreement
Honestly, based on what I learned, whether in the court system or the arb system, people lacking access to significant resources are at a disadvantage in either.
W/o knowing the specifics, it's difficult to provide a definitive answer. Finally, IANAL.