两者都对。to do ...是不定式作 commitment 的定语；to doing ...是介词短语作 commitmen 的定语。比较：
The hospital has a commitment to provide the best possible medical care.
这家医院承诺要提供最好的医疗服务。
The company's commitment to providing quality at a reasonable price has been vital to its success.
这家公司保证供货质优价廉的承诺对它的成功起了决定性有哪些用途。
