I personally think that I would be more noble to dedicate myself to helping one person because I like helping other people. I personally think that I would be more noble to dedicate myself to helping one person because I like seeing that I can help out getting things accomplished.
It all comes down to the greatest overall benefit a person is responsible for at the end of the day. For example, if I had to choose between working to find a cure to cancer or talking one person out of suicide, I would go with the cancer research, because many people die of cancer ever minute, so the faster the cure is found, the more lives are saved, the greater the overall benefit of my work when comparing one person on the verge of death to hundreds in an equally dire circumstance
Although it is very noble and good to help any number of people, I think that it would be more noble if you had a way to work and help a large number of people. This way, a lot more people will be affected and helped, making you more effective.
This was a hard choice, because working to help one person is very noble, e.g.: helping an abandoned child, or a family member who is ailing. But, for the bigger picture it is more noble to help as many people as possible. And we should all aspire to do this.
No, it is not more noble to dedicate oneself to one person than it is to work hard to benefit the many. The needs of the many outweigh the needs of the few, or the one, as was famously stated in Star Trek. While quoting pop culture may seem hokey, the sentiment is correct.
It is noble to help one person just the same as it is noble to benefit many, so choosing one over the other is not bad. However, if you're going for maximum impact I think it is better to benefit many. Generally, one person only needs so much help, but when you speak of groups or masses, the need for help can be far greater.