My company has had bad experiences with Sony, even on warranty service. One laptop (a Vaio) used extensively on field service work had a display failure while on warranty. It took Sony over a month to turn it around.
I would say Dell has better warranty service. Heck, there are guys that drive around all day long doing RMA. They free lance but, make as much as a direct employee.
Sony well, their RMA ain’t so good.