which machineKey config is better?

i 'm working on my web application security and want to know if i use this:           <machineKey validationKey="AutoGenerate,IsolateApps"      compatibilityMode="Framework45"  decryptionKey="AutoGenerate,IsolateApps"      validation="SHA1"/> in my web.config , now first user send first request to my site and in this time validationKey will be create and after that second user send second request now validationkey will be create again or what ? and are the same these validations keys for all user ? what is deference between that config and this?     <machineKey compatibilityMode="Framework45"        validationKey="37BAD4B702C65CF39B1ED514AC4B3D88990DDF784AA0895659      B528ED95F8CA0A9CD1AF5ED92A25993 ...