Rbenv just felt more natural to me. I removed RVM from my system and installed rbenv. I'm not going in the discussion which one is better and why. You can read a good blogpost about the differences and/or similarities here.
To solve the problem with gemsets the blog post mentions also rbenv-gemset which deals with different local gemsets.
There are 2 main ways to do this.
RVM style gem-sets
cd ~/.rbenv/plugins git clone git://github.com/jamis/rbenv-gemset.git rbenv gemset create 1.9.3-p125 helloset >.rbenv-gemsets <<<helloset rbenv gemset active gem install ronn rbenv rehash rbenv gemset list
Project specific gem-sets
I prefer this because If I stop working on a project I can just delete this gemset together with the project.
cd $PROJECT echo '.gems' > .rbenv-gemsets bundle install --path .gems
If you use git don't forget to update your .gitignore to exclude the .gems directory.