SSH tunnel between two OpenWrt routers: sshtunnel vs autossh

I have two routers with OpenWrt and I want to make an ssh tunnel from one router to another to forward remote port. And I want to know how to make it properly.
I can login into the router and make a ssh -R command myself and it works fine. OpenWrt uses Dropbear's dbclient as the ssh client.
But I wan't to make the tunnel working automatically and reconnect on each network failure so I found the sshtunnel but it uses OpenSSH client which is quite large for my 4mb router.
So the first question: why the sshtunnel package can't just work with dropbear? Does the dropbear is so poor on this? Is any important features of openssh client in tunneling that can't be replaced with dropbear?
I found a related thread Set up ssh tunnel, the procd way with a simple init script so it seems like someone uses this approach.
While searching I also found that people also uses autossh for tunneling but I'm not sure if I need it.
If I'll use just a dropbear for port forwarding then do I need the autossh?
Thank you for any your recomendations