Many authors, editors, and publishers appear to feel they should wrap a DRM around their ebook. However, a DRM can be removed from an ebook which appears to only cause an annoyance to the purchaser. That said, do DRM free ebooks provide a better quality to the customer ebook? Do DRM ebooks cause the ebook to be slower and are there any statistics or tests on an ebook with and without a DRM?
This question is a little subjective (is it
better) and broad (there are many different DRM formats).
With that being said, in my personal experience, I prefer DRM-free ebooks. They work better in various readers that support the given document format. I don't always like to use my Sony Reader for books that I purchase (usually epubs). For programming books I often like to use my laptop (either web browser or Calibre) because the programming examples are more difficult to read when shown on a smaller screen that forces line wrapping in unusual places.
DRM Books apply Restrictions on how you can use them (Thats where the name comes from Digital Restriction Management ;-) )
So seen from the author of the book the DRM ebook is better as it allow the author to manage the rights that the user has.
From the point of the reader the non DRM ebooks do not have any restrictions. So you can do whatever you want and the book can not deny it.
If you are a reader and want that your device helps you to not violate the intellectual property rights that the author wants to impose on his work than using a DRM book is better, as you will be sure to only get what the author wants you to have. If the author forgets to grant you rights that you would have then you will not be able to execute these rights.
Another point to take into considerations is that DRM systems might be connected to the company you by the books from. So once this company shuts down it's book selling part or goes completely out of business you could end up in a situation where you can not read the books you bought. This can not happen with DRM free books.
The quality of the anything is judged by its suitability for the task for which it is designed. One of the core design constraints of an ebook is for it to be read. DRM interferes with the ability for the book to be read, which lowers its suitability for which it was designed.
The question then becomes does the value provided by DRM offset the handicaps it imposes. Since DRM provides no value to the consumer, This becomes a trivial question.