*Edited my post after looking up prices*
I am sure that SLS would be much more percise than casting. Also, you do not risk failed attempts with it. With casting, there is lots of opportunity for failure.
Looks like pricing is $10.00 handling fee
$7.00 per cm3
$0.23 per bounding box cm3
$0.45 per surface area cm2.
so a 10cm X 10cm x 10cm piece would run you around $700. I am not sure how that translates to a non-square object or non-solid object but it does not sound cheap.