Easier to read, but harder to understand if what you want is the *other* option.  If there's only one checkbox, then imagine someone who does not want the simple button...they leave the box unchecked...but then there's no indication of what will happen in that case, they know they're not getting the button, but they don't know what they are getting.  It makes them think a lot harder.  They're taking a leap of faith.  Providing both options means that whatever someone's situation, there's something explicitly on screen they can see that reflects what they want, and they can choose it and know what they're getting.

People hunt through interfaces in search of what they want, similar to how people hunt through web pages looking for "the scent of information".  If what they want is represented by the absence of something and isn't explicitly represented, it can be a lot harder to find.  

If you want to tighten up the language, there are usually ways to make the radio button labels shorter, building off a stem sentence or question, ie:

When users add entries to the subform, how many can they add at once?
[ ] One
[ ] One or more

That makes it a bit clearer maybe.  I agree we should keep the language and choices as simple as we can.  But we have to give people a clear choice, so both alternatives are represented.  Individual checkboxes are appropriate only for on/off situations, and this isn't on or off, this is a choice between two different options.  There's been a lot of research on this in usability circles, one example:  http://www.nngroup.com/articles/checkboxes-vs-radio-buttons/