Compare loadDefaultDecorators() in Form/Element.php:

 
    public function loadDefaultDecorators()
    {
        if ($this->loadDefaultDecoratorsIsDisabled()) {
            return;
        }

        $decorators = $this->getDecorators();
        if (empty($decorators)) {
            $this->addDecorator('ViewHelper')
                ->addDecorator('Errors')
                ->addDecorator('Description', array('tag' => 'p', 'class' => 'description'))
                ->addDecorator('HtmlTag', array('tag' => 'dd',
                                               'id'  => $this->getName() . '-element'))
                ->addDecorator('Label', array('tag' => 'dt'));
        }
    }

With Dojo/Form/Element/Dijit.php

    public function loadDefaultDecorators()
    {
        if ($this->loadDefaultDecoratorsIsDisabled()) {
            return;
        }

        $decorators = $this->getDecorators();
        if (empty($decorators)) {
            $this->addDecorator('DijitElement')
                 ->addDecorator('Errors')
                 ->addDecorator('Description', array('tag' => 'p', 'class' => 'description'))
                 ->addDecorator('HtmlTag', array('tag' => 'dd'))
                 ->addDecorator('Label', array('tag' => 'dt'));
        }
    }

The former adds 'id' => $this->getName() . '-element' to the dd HtmlTag, the latter doesn't.