A professional reading would say the number 11. For the three major name numbers and the major birthdate number, the master numbers 11 and 22 aren't reduced to their single-digit expression. Some numerologists also deem 33 to be a master number.

At other numerology chart positions, master numbers are reduced to their single-digit expression; 11 to 2, 22 to 4, and 33 to 6.

Some free numerology readings (and perhaps some paid ones), reduce all numbers to a single digit. It depends on how the software being used is programmed. But a professional reading is unlikely to reduce the master numbers for the major numerology positions.

Regarding accuracy, that would be determined by how close the reading is to the actual you. Because the readings are about tendencies and likelihoods, not about firm predictions or absolute characteristics, accuracy can best be measured by the person the reading is for.

If the question about accuracy was meant to ask which is more applicable, then I think the number 11 would be, as I think would most professional numerologists. But again, it depends on how well it applies to the person you are. Some people express the 11 vibration fully, or nearly so. Others, mostly the 2 vibration.

In numerology, accuracy has to do with the calculations themselves. Although most of the calculations are rather easy arithmetic and relatively simple, an inadvertent mis-calculation could result in a skewed reading. Which is why I use software to do the calculations when it's feasible to do so — software I write myself.

After the calculations are done, the readings for the various calculated results are composed of interpretations of the essence of the energy represented by the number, as related to the number's position in the numerology chart.