What are the advantages/disadvantages of a PhD advisor who is experienced vs. one at the beginning of his career? I know in most of the cases, PhD seekers do not have many options and we must stick to what is offered. However, it happened that I initiated connection with two advisors from different institutes which almost have the same reputation. However, one of them is a lecturer (equivalent to assistant professor in north America) and the other is full professor. Nothing is guaranteed yet, so I won't give up on any of them. Yet, before I delve deeper, I would like to know is it better to work with advisor who is still at the beginning of his academic career but with less experience and maybe more demanding. Or it is better to work with full professor who has long experience but might be too busy for you or not really pushing you to work. 

The answer that I am looking for is from two parts, during PhD study and the future career:

PhD period: I know PhD student is independent researcher and should not rely much on his advisor in many aspects. However, I have this fear due to what I faced during my Master, whereby my supervisor was just looking for the quantity of papers not the quality. I assumed from my conversations with him that the number of publications was main criterion to become full professor in that institute. One the other hand, other colleagues complained about their advisors (full professors) that they really do not allocate enough time for them and even do not encourage them to publish saying that you are master student and this number of publications is enough.

Future career: I assume recommendation letter from full professor outweigh the one from assistant professor. Do you agree? why?
It is sometimes assumed that less experienced / competent supervisor will try harder instead, spending more working time and will be somewhat a friend to you, not just a teacher. However this depends. A younger supervisor may also choose to give you only the minimum required amount of time.

For a good PhD student, it may be most important to get a good project and ideas that, as a rule, work. This does not require lots of time but does require a lot of competence. I would normally select the more experienced supervisor even if one may have less time for me. Only if the studies require some complex, difficult to learn methods, a younger supervisor who still uses these methods directly and personally at work may teach them more efficiently.