While the main aim of S.A.M. and Terra Slicer is to alleviate memory issues by allowing you to use generated slices (in the case of Terra Slicer) or smaller sized Asset Chunks with streaming solutions (like our S.A.M. product), we cannot gaurantee that you will see an improvement in performance. The following breakdown should give you an idea of whether you will see a performance improvement, though please note these are general guidelines and may not be true in all scenarios.
Benefits generally boil down to the following three areas.
1) Higher FPS
2) Lower RAM/memory usage
3) Faster Editor Performance (working on your game is faster).
Keep in mind that the general idea behind S.A.M. and Terra Slicer is to break
your Game World down into smaller slices and chunks, so that you can load only the
portions of the game world that are needed at any given time, both in editor and at
runtime.
For larger game worlds (ones with more objects/assets, not necessarily larger
in physical dimensions), there is more of a benefit to be had.
Think of it like this:
The total size (in terms of number of assets) you load with S.A.M. will remain
relatively fixed (after experimenting to find the right amount).
However, the total size of your game world will likely grow as you add new areas
and such.
If we imagine a formula for calculating the benefit you will receive, it would
like this:
Benefit = Total Game World Size / SAM Load Area Size
So the benefit will grow if the total game world size increases or the area
you are streaming with S.A.M. in a single moment decreases.
If the two are close to the same size the benefit will be small.
This is why you might not see much benefit between a 1000 x 1000 terrain with
no other objects and 4 sliced terrain (each 500 x 500).
The load area in this case is exaxtly the same as the total size of the world.
Terrain wise, you also need to take into account that each Unity Terrain has
overhead. Each uses extra memory and reduces FPS by a bit.
Slicing can offer the following benefits, but only in certain situations:
1) If the region of slices you load is smaller than the original terrain
sources size, the FPS may be better and memory usage lower. Reference the benefit
formula I posted above.
2) The integration of the terrain into the main thread (when it is loaded)
will cause less of an FPS drop the smaller the slices are. This is only a benefit
if you use streaming though. If your source terrain starts in the scene already loaded
this does not matter.
3) Slices allow you to build truly massive worlds of any resolution. Since
terrain have max resolutions, if you use a single terrain you are locked to a max
resolution (around 4096).
This probably doesn't matter to you since your world is only 1000 x 1000.
4) Using slices allows you to change out the textures to support different
biomes while keeping the texture count low. On a single terrain you may need 16+ textures.
Using slices you might be able to get away with 4 different ones.
In conclusion, I hope you can see how difficult it is to predict whether someone
will see benefits while using Terra Slicer and a streaming solution. While it is likely,
there is no guarantee.