Honestly, if your first thought when job searching is "what duties are going to be placed on me," then you should just go with the employed position. Single specialty practices - especially smaller ones - are basically a small business. You do whatever you need to do in order to get referrals, generate revenue, keep overhead low, potentially financial duties such as balancing the books, payroll, etc. These are not really things that others place on you. When you make partner, it's YOUR business. If you don't do those things, the only people who are going to suffer the consequences are you and your partners.
With single specialty, your income potential is VERY high, but the amount of work can be multiple times that of a large health care corporation.