I've seen that user certificates can be stored on the user's computer just like machine certificates would.
I understand it would be very secure if the user had placed his private key on a smart card or USB, cause then it would always be with him, like on his key-ring alongside his house and car keys. So user certificates give him the benefit of being able to log in to the network from any device by using his security token. Perhaps that's the sole point of a user certificate? Idk.
But if you're not using tokens then the user certificate will be installed on the user's computer. That's far less secure than him just using a password to get authorized to the network. He can keep the password as a memorized secret inside his head. But with certificates, he has to store it on the computer. So if someone gets access to his computer he can export the private key. Then voila, that someone can now authenticate to the network with his own device using the certificate and private key he got off someone else's device.
tl;dr: Should you deploy user certificates if you're not planning on using security tokens?