Many believe that the shorter the page the better because it typically means a shorter path to conversion. However, I would strongly encourage testing both long and short approaches. If your upstream messaging is solid, then a short page may be sufficient, but if your paths in lack incomplete messaging, consider a longer approach.
Which ever path you take, consider removing as many leaks as possible – including removing the navigation. Furthermore, make the goal of the page crystal clear by having one single call to action (that’s sufficiently noticeable).
Analyze traffic sources as well – some user segments may perform better when presented with a certain landing page.
In short, there is not hard and fast rule here. Do your homework, understand and address user anxiety, test your hypothesis, and iterate.