744 sim practice
Whilst I agree with previous posters that say that demonstrating good CRM (or 'No-Techs' if you prefer) is the most important factor during the sim assessment, I do not agree that a practice sim is a waste.
The important point is that it is so much easier to demonstrate your good CRM if you are not struggling with basic handling. If you're so focused on trying to 'control the beast', to target an altitude or speed, or sort out the trim on the ILS, it'll be that much harder to have the time and focus to make sure you are doing all the other CRM bits.
Inevitably if it is a new type to you, it takes time to get the feel of the thing and the learning curve is steep - a couple of hours and you feel so much more comfortable handling the thing that suddenly you have the ability to think ahead, consider what is coming up next and plan accordingly.