If we're talking area wise: It really depends. Personally I'd just try to avoid big land areas and especially major cities in this case. If its just above the ocean the changeset size is a lot less relevant.

if we're talking node wise: A lot of imports can have excessive amounts of nodes due to the way they handle things like curves. So reducing the amounts can be benificial. I think that could also be the case here. I tried simplifying a few area's you added (shift+y in josm) and could reduce the amount of nodes by 50% (by selecting 0.5m) and it didnt really make much of a visual impact unless I zoomed in as much as possible. 

I also noticed you had a few pixellated areas. Might be worth looking in to. 
https://www.openstreetmap.org/way/1184351223
https://www.openstreetmap.org/relation/16009408
