that depends on how you are querying. If you are always query columns
individually (or columns x and y together or z, but never x,y,z ) you will
benefit from the split. Also if column z is largely empty you will get
little benefit. The more data in column z the better the benefit by
splitting it off into another table.

THX Kasper,
Unless Full Text Search queries are the MAJOR functionality that these
tables are used for, i.e.., there are no other SQL Server queries, I would
not base your decision to split the table based sole upon FTS. For SQL FT
Indexing and FT Search queries, the primary factor is the number of rows in
the table, and unless your splitting the table into more than one table
reduces the number of rows, I would not recommend splitting the tables. Many
years ago, Microsoft ran a series of performance tests matrix on the same
data with a "tall" or many rows & "narrow" or small amount of text  vs. a
"wide" or a  large amount of text and "short" or few number of rows. The
overall conclusion was that FTS performed better with short, narrow tables,
and the most significant factor was the number of rows. I'd highly recommend
that you only consider splitting the tables, based upon other criteria,
unless splitting the tables reduces the overall number of rows that are FT
Indexed.

Regards,
John