A couple thoughts on the swing and pushup coupling:
1. Both free weight and bodyweight balance.
2. No overhead room needed (this is actually something that matters in some homes - I like my basement for working out but it has low ceilings, so no TGUs possible but swings are fine)
3. A push and a pull, full body both
4. A bend and a rigidity
5. Only one kettlebell needed at a time - I've got two sizes for S&S, one for swings and one for TGUs
6. TGUs are epic and heroic, but I think the good ole pushup loads more weight onto you