What are the cons of studying in a Ph.D. program that takes much time to confer the degree (about 1 year and a half or 2 years, after dissertation)?
Many academic positions after graduation are dependent on proof of degree completion, so this could potentially be a problem.  The NSF math postdocs, for example, require a signature from the school that you've completed your degree, and some positions explicitly require a copy of your transcript or diploma that indicate your completion of a Ph.D. program.  The institution where I completed a postdoc was in this latter category, and would only issue an informal offer (and not an official contract) until they received final documentation of my degree, which in my case took several months to arrive after graduation.  One practical problem I faced as a result was difficulty arranging for housing at my postdoc institution; most rental companies want to see their tenant's signed contract as proof of income.  I am also aware of tenure track jobs where the contract specified that the tenure clock only started after conferral of a degree.  I suspect some institutions would be willing to bend the rules a bit in unusual circumstances, but it certainly could be a problem.  (Note that this answer is based on experiences of myself and colleagues in the US.  I have no idea how this practice varies in other countries.)