There is a wide range of opinions on this question. The
determining factor with DSL is how close you live to the DSlam.
The further away you are, the slower the speed. Distance does
not affect cable internet access.
Some will tell you that as more users in your neighborhood log on
to the internet, speed will decrease. Where I live I find that
to be untrue.
Your DSL or cable provider may provide a poorly designed and
maintained system or a great system. All providers are not
equal.
The answer then is dependent upon your individual circumstance.