I sure think both are critical as far as your blog success is concerned. The trick though is to learn the delicate art of treating each of them differently while at the same time making sure that they both understand that they are important and that they do matter.
Another way to understand the importance and relevancy of each of these group is to look at what level your blog is as far as growth is concerned. When starting out, it is easy to manage comments and carry on the conversation but as traffic grows it soon becomes unmanageable and it's common to see that most successful bloggers end up closing out the comment feature. Of course at this time you subscribers number can unlock many doors and opportunities.