Like several PPs say, I don't think it's possible to say what's "better" on a grand scale. There are reasons for making either choice--life often just "happens".
I wouldn't have minded having children in my 20s--in fact, I probably would have, had I met someone who would have been a suitable partner. (I didn't want to--and still don't want to--raise children alone--but admire those who do.)
But I went through a series of major personal transformations in my beliefs, actions, and activities in my mid- to late-20s, which included major dietary changes, a discovery of the wonders of exercise, an abundance of international travel, and learning about a lot of ideas I had never encountered before.
Could I have done all this with children? I suppose yes, I could have. But it probably would have been much more complicated, and maybe my attentions would have been focused elsewhere and I wouldn't have even thought to make the changes. Does it really matter? It only does to me now--it wouldn't if it hadn't happened.
Catherine, mama to Preschooler Girl 9/08, and Toddler Boy 3/11