I'm going to go out on a short limb here and say: XML is an even worse idea than EAV. EAV Creates a weak data type design while XML creates a non-normalized weak data type design. You would never design a table that had a field Person that contained this: "FirstName: John; LastName: Doe; BirthDate: 1/1/1980"
So why would you want a field that contained " "
If you have to have customizable fields for searching or reporting purposes, fine, create an EAV table or two for that purpose. But don't design major parts of your database that way.