There are many types/ways to purchase Disability coverage:
Short vs Long Term - do you want to be paid immediately for a 90 days or want to wait 90+ days but get paid until retirement age
Individual Plans - 1099 or W2 Employees. Plans owned by the individual and therefore controlled by you. This can be done to augment current coverage or to lock in current health/income in anticipation of a move.
Group Discounts - ANY of you with 3 colleagues interested (don't even have to know each other!) qualify for a retroactive discount. In addition certain professions or members of professional organizations qualify for discounts.
Women take note: In many cases these are 2x discounts utilizing Unisex rates and % off premium
Supplemental - If a large % of your income is derived from bonuses or gratuities then I would urge you to check your group plan. Most ONLY COVER BASE SALARY! A supplemental plan would make up the difference between your true income qualification and what the group plan pays on.
Supplemental 2 - If you are a highly paid individual your group plan may be capped. If you make $300k/year but have a $10k/month cap on benefits then you don't have the 60% coverage the HR handout says you do
Group Plans - Whether true group or voluntary it is inexpensive or even free to the Employer to make coverage available to your staff. Why wouldn't you help your clients protect themselves (and probably reduce Worker's Comp claims in the process!)?