Compared to deferred rendering that is. There seems to be very little on this.
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We just switched in the middle of a project to forward rendering and virtually no difference in appearance for maybe 15-20% FPS improvement. Allegedly it supports “fewer shader options” but our fanciest shader is volumetric fog which still works perfectly.
Anyway, changing over is just a single project setting and wait for shaders to compile. Easy to test it for a week and change back if any issues. 
Did you read the documentation?
https://docs.unrealengine.com/en-us/…orwardRenderer
It definitely effects some translucent materials but there’s a lot going on that it changes. You also lose the ability to write out frames from buffers (passes) because of the way the final image is generated in forward shading. This is guarenteed to break materials that rely on “SceneTexture” nodes.
We have noticed an increase in FPS performance, which is really not a true indication of performance in UE4, as to resources that would benefit from forward rendering in the first place.
Shader complexity seems to be less critical and more so in the area of transparency.
The use of sub surface profiles is out
Landscape materials tends to create missing texture errors requiring they be switched to shared wrap.
Ambient cube maps (HDRI) do not work in FR.
Consideration for use.
If your game has an on line component or plan on using VR any performance bump is desirable and to this point working around some of the feature issues is a matter of finding a different way of doing something.
If your game is stand alone and able to maintain a height performance curve then I would consider to defer the switch until the game is in the final polish stage and can be properly tested and profile as being fit to finish.
Personal opinion as to looks?
Some say FR looks better but I would suggest that it only looks different and neither better or worse.
We just switched for forward rendering for our VR project and it was an eye opener… the graphics are just so much crisper and sharper with MSAA than with TAA.
We haven’t measured the performance difference yet, but it seems better. The appearance is night and day, though. I think we will stay with forward.
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The biggest loss is SSAO, which can be a deal breaker if your visuals depend on it.
SSAO can be a very muddy specially on moving objects. I don’t miss it in forward : )
Forward pros for us:
1 - MSAA over TAA sharper images and better on moving objects.
2 - performance boost depending what you are doing.
Cons:
1 - Decal support suffers.
2 - No SSS profile for skin.
3 - Begging Epic to fix the first point for at least a year now :).
Hmm… what is the difference between SSAO and regular AO? Because I can clearly see some AO in forward mode, even though it is very noisy compared to deferred TAA.
Lack of decal support is worrysome, though.
SSAO works in forward rendering now.
Indeed, that’s the biggest issue. For me, its a deal breaker.
It works with forward rendering, but only if you use TAA, not if you use MSAA. Being able to use MSAA is the main reason for forward rendering though. And then SSAO does not work, since the UE4 SSAO has no blur pass, it completely relies on TAA.
Good vid on faking SSR with a forward rendering shader in Unreal with a guy from AMD and an intro from a guy from Pixar 
rOb
I suppose you mean SSS, yes I ahve seen it, unfortunately the results aren’t anywhere near SSS profile with deffered, anyway SSS in Forward can be faked though using pre-integrated skin shader and a few other tricks.
Unfortunately epic seems to be neglecting forward ever since the VR buzz died down, at least something came out of it though, I can’t imagine working with deffered doing what i’m doing right now.