based on plan alone, i'd go with cingular, they have unlimited talk between cingular customers on $39+ plans, unlimited nights and weekends on plans $49+ rollover minutes on plans over $39, and for plans of $59 or higher, the extra line is $9.99. The $59 nation plan from cingular has 850 anytime minutes, and the extra line would be $9.99
however, if cingular doesn't have good reception in your area, i would look at other carriers.