Parliamentarism is certainly better than presidentialism in the abstract, if by presidentialism is meant a one-person office. (Collective presidencies have their merits). But in a deeply divided place it is just as important to consider how to create a properly collegial cabinet, under either parliamentarism (which can be combined with an overly powerful Prime Minister) or presidentialism. The electoral system is just as  important: list-PR will likely be the most suitable option in Burma. For more information see J. McEvoy and B. O'Leary (eds). Power-sharing in Deeply Divided Places, and A. Lijphart Thinking About Democracy. So-called semi-presidentialism (the French model) is not to be recommended: its sole use in a deeply divided place that I know of is in Sri Lanka. In Burma it would ensure permanent Burman domination. Enough said. 

O'Leary and Lijphart are the deans on this subject of course. I would add, as a mere observer of this area of inquiry, that I find Lijphart's concept of consociationalism (and its critics) a good place to start. It is now an old concept, but it was coined to think through governance issues in deeply divided societies like Northern Ireland and the Netherlands.

I think it might be worth looking at the situation in South Africa and in particular the 1994 consitution.

Regarding this sensitive and very controversial issue please find a publication of International Idea. Constitutional Transitions and Territorial Cleavages

George Anderson and Sujit Choudhry Edited by Sumit Bisarya, International IDEA Constitution Building Programme

http://www.idea.int/publications/constitutional-transitions/loader.cfm?csModule=security/getfile&pageID=70302

I hope you will find possible pertinent answers here.

Sincerely,

K.G.