Just curious what others have found to be the most effective tool for creating functional lightmaps within complex geometry.
I’ve used 3ds Max exclusively for years, even without tapping into more recent things like Steamroller, but have found myself now working a LOT with 3DCoat.
Curious what others have found to be the most effective for generating lightmaps with reasonable efficiency.
To render lightmaps there currently only is Unreal Lightmass compatible.
But I guess what you actually mean are the lightmap UV coordinates you create in your favorite DDC tool. 
For that it really depends on your preferences. I for one recently moved on from 3ds max to Modo and use its Atlas tool to get me started. Then I rearrange the UVs by hand until I’m happy with the result. To help with packing of the UVs Warren Marshall recommends the tool iPackThat in his video here . While I haven’t used it myself yet, what he shows though looks promising to me.
Have fun UVing