Preferred Update Method?

I load my grid:

d = new Array()
d = [[blah blah]..]
obj.setCellText(d)

Later, I want to update a row. Which is preferred?

d[somerow] = newdata
obj.refresh()

or

for (i=0;i<colcount;i++) {
obj.setCellText("stuff",i,somerow)
}
obj.refresh()

In both cases, however, the grid display does not properly refresh.