I am currently working on improving a donation task flow which is similar to the ones of the major crowd-sourcing platforms, however, there are no donation tiers involved, just dollar amounts.
As always, the user gets to browse the project page and then decides to donate or not. Now, modal or single screen after the user has clicked the call-to-action donation button?
To me, the modal has an edge because the donation itself has strong context to the project, which is underneath the modal. Also, I do not want to take the user away from the project page making him feel isolated and insecure. A modal also feels lighter and quicker to me, making it faster and seemingly more uncomplicated to donate.
I think Facebook has done a really great job with their modal donation approach for the Philippines campaign, in case someone has seen this.
I have not done any usability testing with the two different approaches I have yet, however, planing to do so.
I would definitely be interested to hear your take on this.