I hope this is not a politically incorrect question to ask, but for a PhD student who usually publishes at CCC/ITCS/ICALP (and occasionally at FOCS/STOC), could it be harmful (career-wise) to publish less significant works in less prestigious conferences (e.g. MFCS, FCT, STACS, IPL)? Could it be better to just leave such papers laying at ECCC/arXiv? 
Is it sometimes better to not publish at all?
soft question;career