mercurial and git

I am experimenting mercurial and git for distributed version control system. Both are nice. From my point of views the main pros and cons are as follows
mercurial :
pros: single binary
cons: bit slower that git
git :
pros : fast
cons: placed some 130 binaries in my bin

I will keep updating it with increase in my experience with them.
one thing that distributed version control lacks is the ability to restrict someone to work on a particular module. lets see if i can find out some way or is this really a restriction. Surely not for the open source world.