which machineKey config is better?

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
B528ED95F8CA0A9CD1AF5ED92A2599362684CB8D204AC30D07E6BF0CF65194A5129"
decryptionKey="B450FB3271C49E6BA89A0C5C8D06B61875BCE4916A40474ED"
validation="SHA1" decryption="AES" />
which one is better to use?