With worklight 6.2 the client devices send logs to the server automatically with a adapter invocation or a connect call (this is configurable however it's on by default).
What I'm asking is if there is any performance decrease (or opinion from IBM) with this operation as it seems a heavy process that scales with the number of devices in our network.
Unfortunately there is no one answer to this question as it depends on your server load. If you only have 100 active users connecting to your server, then this probably isn't a big deal. If you have several million connecting, then it might be a good idea to disable the auto send features and then use the dynamic logger configuration on the server to enable it when you actually want the logs.
You'll have to run tests for your specific server load to really know how this would affect your server