Blog de Alejandro Avila

source: http://social.msdn.microsoft.com/Forums/en-SG/sharepointdevelopment/thread/54119d99-0f25-41ed-b91c-5ac6ad84bcd7

 

The FullTextSQLQuery has the advantages of pulling data from across multiple site collections/web applications and is very fast when searching compared to the SPSiteDataQuery. The only problems are the timeliness of the data and the use of the "OR" operator. Depending on how often you are crawling (incremental) users will not see changes immediately. This becomes an issue when users want to see status or if a document is checked out.  FullTextSQLQuery does not track whether a crawled property is null. Null values are not stored. Therefore if you OR two managed properties together and there is not a value for both, then the record will not be returned. You can use the PATH managed property for url navigation. FullTextSQLQuery also gives more options for searching such as full text searching.

 

source: http://social.msdn.microsoft.com/Forums/en-SG/sharepointdevelopment/thread/54119d99-0f25-41ed-b91c-5ac6ad84bcd7