Hello!
Can anyone experienced look at this:
and tell if elements with “landuse=grass” are OK or there are too much of them here.
This:
in real life looks the same, but on map there is almost no grass.
So which looks better? Which should be changed to look more like the other one?
Hello from Germany 
!
For me, there’s nothing wrong with mapping grass, after all, there’s no private garden involved, but largely public space (even if some of it is certainly only accessible to tenants).
However, ‘mapping by beauty’ is not the purpose of OSM, because it is initially ‘only’ a database. What the renderers make of it is at their discretion. You can see this if you go to the main page of the map and compare the map layers on the right-hand side - there are an infinite number of other variants on the www…
Greetings 
Andreas
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I asked because “grass” and “residential” are both values of “landuse” parameter. IMHO one place can have only one landuse. And example above is different. I also can understand difference between OSM data and it’s renders. Or maybe proper solution is to just cutout grass from residential area?
“grass” isn’t actually a landUSE but more of a landcover, but that’s one of the inconsistencies we have to live with. So it’s correct to overlap landuse=residential + landuse=grass, but not so much landuse=residential + landuse=farmland
see also Key:landuse - OpenStreetMap Wiki
Note: At least two of the common values of landuse=* may be viewed as not strictly land use. These are landuse=grass and landuse=forest. Please refer to the pages of these for more information.
Actually, you’re right. But landuse=grass is one of the many exceptions that is simply used for “grass grows here (and is mowed regularly)”.
The alternative landcover=grass has not caught on.
The question should not be which tagging looks better in the OSM standard map, but which kind of surface is there in reality. As others have said it is quite ok to tag landuse=grass on top of an area with landuse=residential, but as far as I can see most of the areas are not covered with grass, but with shrubbery, trees, some flowerbeds and hedges and the like.
So mapping all of this as “grass” is definitely not correct. If I do not have the time and the energy to map these places in detail according to the vegetation being present I would prefer to just leave this as landuse=residential only without adding any further landuse or landcover tag at all.
By the way it is also possible to tag grassy areas included in another landuse as landcover=grass which is not as popular as landuse=grass but still has some 50K uses according to taginfo.
“Landcover” seems to be better here than “landuse”. Thank you all!
@Map_HeRo I asked what looks better from data perspective, not as rendered image 
… for the benefit of anyone new to the topic, “landcover vs landuse” is an OSM “big-endian vs little-endian” debate that seems to have been going on since about 1726. It’s unlikely that the more extreme proponents of either side will convince the other; the status quo is that some people use landcover keys for features; many consumers ignore them, but some don’t.