I have a pretty big set of kettlebells (competition bells from 8 kg to 40 kg, and doubles at 16 and 24), a pair of Indian clubs, a macebell, and an Adex adjustable club.
I find clubs and kettlebells to be natural complements to each other, very good at different things, but not substitutable goods.
What clubs and maces add to the party are cross-body movements (mills) and big circular shoulder movements (macebell 360 and 10-2).
If I'm ever pressed for time or need something portable:
--KB swings
--KB clean & press
--Macebell 360
That gets a lot done very quickly and I can do it in the park.