Having done both Pomodoro and 30/30, I feel that the ideal is a mix between the two.
Pomodoro is ideal for mindless tasks where you want to churn out as much time as possible. It's also perfect at maintaining momentum. Pomodoro actually works great for light programming as it forces you to take a little stretch or tea break.
Tasks where you want to maintain full concentration work well with Pomodoros, but it takes a little practice to change your 5 minute break into something that doesn't disrupt focus. For example, if you're in the flow, just take a short walk to run the idea in your head.
The downside of the Pomodoro is that it can be exhausting. With some tasks, you'll reach a breaking point where the 5/15 min breaks are not nearly enough, and you'll start to disrespect the Pomodoro's time limits.
30/30 is ideal for creative tasks and learning tasks. The 30 minute break is ideal for your mind to 'settle' what you've learned or to calm yourself and listen to your intuition. After some very difficult tasks, you'll want to force some time off; the 30/30 rule keeps that time off from exceeding the time you spent working.
Many people can barely do 8 pomodoros a 8 hour workday. If you find yourself doing so, you should consider the 30/30 cycle.
Also note that the 30 min break doesn't have to be unproductive. I often reserve it for mindless, but necessary tasks like filtering e-mail or doing paperwork.
At the very least, 30/30 makes for a very productive, yet relaxing weekend for workaholics.
I'd recommend for most people to try both and learn to swap between the two techniques. They're both tools, suitable for different situations.