Continuing today's line of Lars.
Quick Answer is the same as for amount PS or % of recurrings : WHATEVER PROGRAM SENDS YOU THE BIGGETS CHECK FOR YOUR TRAFFIC...
Pay attention not to the ratio of program, but to the amount of money you get from it. You may compare ratios only if the conditions for counting it are the same for different programs. It always makes me wonder when I see topics with "My last month ratio stats for sponsors". If you track the clicks from your side and then count the amount per click you get from the program, it's OK, but if you use sponsor stats to get clicks data - it's totally unacceptable. Some of the programs count only join hits, others redirect (and don't count) hits 'chinese' traffic etc.
Even if you count the hits and your revenue by the same way for different programs, you also should remember about the amount of traffic you may send to program.
Is it better to have 1,000 uniques per month and have 1/100 ratio OR 10,000 uniques and 1/200? Last option will make you more revenue.