"..." syntax needs to escape more characters. "..." makes a processing into the text, so i think it worse. All the $1 parameters we use may need to be escaped to $ to avoid php looking for a variable called $1 (or even give an error, as variable names need to start with a letter or underscore). $1 is not currently affected, but {$1} do need (think in templates).
And although writing wikitext can be horrible, it can also be difficult to write html into "..." (due to html params).