Your choice here will solely depend on how much crepes you place to produce. If you need to create a high volume within a short time, a dual griddle unit would be a much preferable choice.
The only downside is that it may end up taking more space, so you must ensure you have enough counter space to accommodate it. However, if you are planning to serve only a limited selection or if you have a small restaurant, then a single griddle crepe is ideal.