cable (optus/telstra) is 10mbit
adsl is 1.5mbit
which is, theoretically:
cable: 1250KB/s
adsl: 187.5KB/s
these are maximum values however.
i'm on telstra bigpond cable (3gb, yes... it sucks)
but my maximum single (no jets, no mirrors, no splitting/segmenting) download speed was about 1MB/s creeping up to 1.1MB/s
generally hitting 800-900KB/s
adsl is a 'better' deal, if you want more quota.
e.g. 10-12GB a month, instead of the lousy 3 from optus/telstra.
reliability is another issue,
availability is as well.
but overall, i'm on cable because i've been with telstra for about 4-5 years now, and it gives me fast internet access (at the cost of having a 3gb limit per month).
if you want 50-60KB/s transfers, go with adsl and get a larger quota