“in a place where Baalei Teshuva stand even Tzadikim who are complete cannot have room for their feet”
Every complete tzaddik is a baal teshuva. If he is a genuine tzaddik he is constantly making a cheshbon hanefesh and doing teshuva.
“Which is better, kiruv or kollel?”
Whichever you think will bring you closer to Hashem and to fulfilling your tafkid is better for you.