Agreed. Vouches gives more trust than donations. We are all Human though and even someone who has been on this forum for 5 years can be banned on 1 false trade.
To be honest I donated and for 2 reasons
1. I'm on this site everyday and want to support it
2. Having a title/custom user name does make you stand out from the pack as a verified user and most members are more than likely to trade with you based on that.
As stated a GAJILLION times the choice is yours. Whether you do or don't it's all based on personal preference.
The $100 would make you look more trusted as you are less likely to scam as you would be losing the account with the $100 donation but vouches are still make you look more trusted than anything tbh.