One of the benefits is that you will not loose the traffic. Regarding link juice, a 301 is a permanent redirect so everything goes to the final page. Or at least, that how it used to be. I haven’t checked in a while but I doubt this has changed since, as I already said, the redirect is permanent.
From the SEO point of view, there’s very little difference between direct traffic and permanently redirected. You could find very small differences but this is due to lots of factors.
As an example, part of your ranking is due to the traffic your receive. A redirect always takes a few milliseconds more to load because it needs to transfer the web page petition. If there’s any problem in the server, those milliseconds may be seconds, and that may mean some lost traffic.
Of course, this normally doesn’t happen and I’m exaggerating a bit. If could happen, of course, but it is very unusual. What I mean is that while there difference is minimal, there is some difference between direct traffic and redirect.
I will add to this that, in my humble opinion, thinking in terms of SEO is just wrong. When I buy more than one version of a domain is because there’s some benefit for my viewers/visitors or because I need to protect that domain.