What matters most while choosing a lab for PhD?

I have been selected for PhD program in life sciences at a local university near my home. I have gone there and the labs are pretty good. The research scholars in the lab work very hard till late in the night everyday and sometimes in the weekends also. The work going on in the lab is good and matches my interests. However, they do not have many publications. I am a little ambitious and would like to try for better institutes that have far better publications but getting there is tough. I need to take a risk of losing my current position to try for PhD elsewhere. Is it worth taking the risk?