Should I choose an tenured advisor good at research but bad at teaching or an untenured professor good at teaching? I have a Phd option with two professors. 

Professor A is tenured and is doing  very good in research .But many people have complained against him that they cannot understand his class. He has 2 Phd Students -one has been working on Phd for 5 years but still hasn't given his candidature. The other student joined his lab in 2012 as Masters Student and is planning to graduate from Phd in 2016. He closely works with corporate and is very well funded and pays his students very high stipends (like 3k+).These students regularly go for internships in these companies. But i see these students working very long hours on weekdays and weekends to complete their class and research projects.He was recently made an distinguished professor of research in my university.

Professor B has been in university for 3 years and has just graduated a PhD student(after 3 years). He is looking for tenure and is very prolific publisher. However he also published to some questionable open access journals  (one's included in Beall's List) to achieve his tenure requirements. There are  3 students in his lab -2 Master's and one 20 hr working CS student to help them out with programming. He has few projects to work on but not as big as tenured professor's. But people have high hopes on this professor as he worked in industry for 6 years prior to becoming an assistant professor.He is also very a good teacher .His Phd student could not get a job in his research field and is now working as a full time research software developer.

Which professor should i choose for an Phd and what should i look out for in each of them like pitfalls and advantages .
I'm not sure why a professor's capabilities as a lecturer should have anything to do when considering her competencies as a mentor and research advisor. The two skill sets are almost completely separate from one another. Moreover, if part of your concern is that you want to become a teaching faculty member some day, then there's probably a chance to be a teaching assistant for another faculty member who is more qualified as a teacher (such as your Professor B).