Depends on your application, each similar looking commands are different commands for different reasons.
http://docs.blynk.cc/#blynk-firmware-connection-management-blynkconnect
BLYNK_CONNECTED() {
// Your code here gets ran each time Blynk connects to the server i.e. after a disconnection
}
http://docs.blynk.cc/#blynk-firmware-virtual-pins-control-blynk_connected
http://docs.blynk.cc/#blynk-firmware-connection-management-blynkconnect
void loop()
{
if (Blynk.connected()) {
Blynk.run(); // only runs this command if connected to server
} else {
Blynk.connect(); // this command will attempt to reconnect, only if disconnected, with default timeout of 30 seconds
// perhaps better ran in a timed loop every 5min or so
}
timer.run(); // runs this command all the time
}