I would say what matters is your personal profiles.

e-Rewards is about market research. To be more specific, I think it's more geared toward business management/executives) and technology. Some high-value surveys are targeted toward these clientile. If you don't fit the profile, you won't get survey. If you don't fit their screening criteria, you don't get to finish the survey and no full credit.

The the best of my knowledge, e-Rewards sponsors may only affect your redemption options. Certain sponsors only allow you to redeem for certain FFPs, such as Delta, NW, e-Miles...etc. Some are less restrictive.

Look around our SPAM Forum, there are quite a few (long) e-Rewards threads on this very topic (sponsors & redemption restircitions).