Are contest links better than site support links?
They do cost some but only a little (e.g. if 5 members get 25c, the total cost is $1.25 vs. a regular paid ad: if 1000 members get 1c, the total cost is $10; or the price could be a referral or ad).
(And if they are sold for cash, instead of sent by the site owner, then they earn him/her that way, unless if they are underpriced, but I think they don't have to be because of the low cost to him/her.)
They probably have a better clickthrough rate.
Members who do click them are rewarded for their effort if they get lucky.

edited: btw. I don't like contest links that only earn you less than 25c if you finally get lucky and win one. (above that it's ok because your chances of winning can be higher with a lower price amount - e.g. 4 people could win 25c or 1 person $1, with the former option the chance of winning would be 4x as high)

A support link as a contest link is always more successful I think, than just a support link, because you maybe get a little gift for your supporting...
But I must say for my point: I try to click so many revenue, support links as possible, because I think that the progs I'm in deserve a little support ...
another think is: to present a support link as a cheap link, this works, too, sometimes

I always ignore both links.

Im not real big on either of them but I do click on site support links and most of the time I click contest links too.