Best Of

Ive just run a series of pretty exhaustive tests with simplygon 10 vs manual lods on a load of characters
(we already know it can't cope with hard surface meshes so didn't bother there)

TLDR :
You'll get a better looking result doing it by hand for the same geometry cost - especially on the lowest lods
Simplygon still can't give you a one size fits all solution because it's still using a % of input mesh metric to determine how much to reduce something by (which is extremely wrong). 

On the other hand..
Because the SDK exists now I'm able to generate acceptable lods for over 100 pre-skinned character body parts in 10 minutes,  i'm able to do it over and over again with different settings and i'm able to integrate it into our export pipeline. 

It's a tradeoff - I'd rather ship with suboptimal auto lods and only get 90% of the performance than have no lods for 80% of the dev cycle and ruin any hope we have of gauging how well the game runs.

Auto LOD is included in every major game engine and it can be good enough in most cases until it isn´t anymore.
Like for example eyes or hair pieces which are suddenly missing. (these four examples show an active Auto LOD without the included Distance where it occurs)

Depending on when those issues pop up, you could do some educated guesses on what Method to choose.
Mixing Auto LOD and having other meshes in the same scene using Manual LOD works. Doing this reduces the needed amount of work.

I haven´t looked into this yet but it might be even possible to mix AutoLOD and manual LOD depending on the ranges you set. This would drastically lower the amount of needed manual LODs.