Well, You might notice the pokemon being slightly weaker in those games that in the Main Stream Pokemon games.
Its because in The Mystery Dungeon games there are no Ev's and there are set natures.
Here is a link to a Guide on what starters are what nature
Aside from that, Pokemon You get afterwards don't have set natures, but its just the same as base stats, with No ev's.
And IV's do still Exist, so keep that in mind.