Are you asking HDMI/DVI vs component?
The advantage of the digital connection is that the digital DVD signal doesn't have to get converted to analog before being reconverted to digital (then scaled) at the TV. The difference is often not that noticable.
With a digital connection, sometimes the DVD player does better, sometimes the TV. Some people even select 480i because the TV has a better deinterlacer.
There can be issues with feeding a 1080i TV a 720p signal. Some of the earlier models were know to downconvert 720p to 540 then upconvert back to 1080.