Yes, the battery drain on iOS is also the thing stopping me from having it on my iPhone. Wireguard is way better in that regard, but has other issues (e.g. no split dns, no dns re-resolve for dyndns or for network changes).
Other than that tailscale is really great. It just works.
Less battery life on your iPhone. :)
I have both in my home network and love both.
At work, I have used Tailscale in my Kubernetes clusters to allow devs to get into the private subnets, so that is awesome, and way better than trying to give a group wireguard key pairs.