The older you get, the more you've got to lose, and a lot of people become less radical with age.
At the same time you also tend to be a higher value target for external actors compared to young, new, members of an organisation. So in the young end of it you'd prefer infiltration to recruiting informants, in part because young informants also tend to be less reliable than old, for the reasons above. If it's your agent loyalty isn't as brittle as when you've convinced someone to become a traitor.
When news of government or other external actors having gained access breaks, you typically don't want your infiltrators to become known if you can avoid it. It's different in some settings, antifascists commonly do the opposite and try to protect their informants so they can keep working if they move on to another far right group, while their infiltrators sometimes go public with what they've done.
At the same time you also tend to be a higher value target for external actors compared to young, new, members of an organisation. So in the young end of it you'd prefer infiltration to recruiting informants, in part because young informants also tend to be less reliable than old, for the reasons above. If it's your agent loyalty isn't as brittle as when you've convinced someone to become a traitor.
When news of government or other external actors having gained access breaks, you typically don't want your infiltrators to become known if you can avoid it. It's different in some settings, antifascists commonly do the opposite and try to protect their informants so they can keep working if they move on to another far right group, while their infiltrators sometimes go public with what they've done.