Yeah, the argument being made by those authorities is stronger than your "nuh-uh" rebuttal.
The argument, at least based on my casual reading, is that a parlimentarian system allows a prime minister to have majority support. This allows legislation to move forward without the sort of gridlock possible in our system but not in a tyrannical manner

rolleyes

. Gridlock is possible but there are democratic outs to keep things functional that don't exist in our system. Ultimately presidential systems can run to absolute gridlock at which time coups either in support of the president or the legislation occur. Alternatively legislative procedural processes can be put in place that neuter the executive branch (and, often, the second smaller legislative body). Either way the system breaks.
Our own system is further burdened by Duvegnier's Principle which pretty much guarentees that we'll keep a two party system regardless of what those parties are.
You can read some of Linz's discussion at:
http://www1.american.edu/ia/cdem/pdfs/linz_perils_presidencialism.pdf