It was mainly a matter of time it would take to customize the survey.
The PHP Classes site already has a basic poll system that was used in the design contest organized in 2009/2010 to pick a new design for the site from proposals submitted by the users.
The problem is that it would take a good time to customize the voting system for this type of survey.
Another aspect is that Google Forms have a nice way of presenting the results that is ready to use when the results are published.
Finally I wanted to open the survey process to non-PHP Classes users, so nobody needed to have an account in the site to participate.
Users would need to have an account somewhere, so the system prevents users participating more than once and distort the results.
Whatever system was used, I suspect there would be probably some complaints.
Anyway, I was not aware Google would have so much rejection. If there is some other system that has less rejection, I would appreciate suggestions, as there may be other surveys in the future.