What are the pros and cons of publishing a new unpublished idea in a poster session in a leading conference?
In my field (in computer science), posters are usually a &quot;low cost, low benefit&quot; activity.
Pro:

A small amount of visibility
A small but nice CV entry
A small opportunity for feedback and input

Cons:

A small time investment for actually developing the poster and, sometimes, writing up an accompanying paper
A small cost for registering at the conference (I assume that the conference will be online due to COVID19, otherwise the costs could actually be larger)

In the end, it probably won't make much of a difference, unless lightning strikes and you happen to get amazing input/feedback/collaboration opportunities (not impossible to happen but unlikely).