It depends on just what you want to do. BaseCamp can do a lot of stuff other than route planning.
My main use is for viewing tracks recorded on my GPS, looking at them on the map and analysing the statistics.
Also I have various collections of waypoints for places of interest, so its nice to see them on a map and decide which to visit.
And managing the waypoints/routes/tracks on the GPS device. I can figure out which ones I want to delete/edit, or download them all as a backup.
BaseCamp also has features for geotagging photos, and geocaching/opencaching, if you care about that.
In terms of route planning, it can do a few things that are not possible in Bikehike etc. eg you can view several different routes/tracks at once, so you can check if they are going the same way etc. Also you can split and join routes/tracks, which is handy if you want to reuse sections of a previous route.