|So there would be no loss of signal which ever way i do it.?|
There shouldn't be.
As I said, ADSL works through a phone line. Phone lines can far exceed the maximum segment length of a Cat5e (or 6) network cable. They (network cables) are limited to 100 metres.
Since you're only having to span 20 m you could as easily use a network cable as a phone cable. The big question is, which is going to be easier.......one phone cable, or two network cables?
Go with whatever is easiest and makes the most sense to you. If it were me, I'd go with running the one phone cable.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.