1. Advantages for you.
Limited contracts - higher gratuity payment, potential financial penalty for company if they attempt to terminate your before contract expires.
Unlimited contracts - more flexible since you only have to give one month notice if you want to leave.
Disadvantages for you
Limited contracts - you are committed for a fixed period of time, potential one year ban and loss of gratuity if you break limited contract.
Unlimited contracts - can be given just one month notice by company, lower gratuity.
2. You should only sign papers you understand and agree with. Contact the Dubai labour department
and/or a lawyer if there is anything that you don't understand, or are not sure if it is acceptable.