gem vs bundle exec environment differences

capistrano settings

require "bundler/capistrano"
require "rvm/capistrano"
set :rvm_ruby_string, "ruby-1.9.2-p290"
set :bundle_dir, '/usr/local/rvm/gems/ruby-1.9.2-p290'

Capistrano then executes this command:
bundle install --gemfile /home/deploy/rails_app/releases/20120403233447/Gemfile --path /usr/local/rvm/gems/ruby-1.9.2-p290 --deployment --quiet --without development test"

environment output

$ rvm list

rvm rubies

=* ruby-1.9.2-p290 [ x86_64 ]

# => - current
# =* - current && default
#  * - default

[deploy@staging01 current]$ gem environment
RubyGems Environment:
  - RUBYGEMS VERSION: 1.8.21
  - RUBY VERSION: 1.9.2 (2011-07-09 patchlevel 290) [x86_64-linux]
  - INSTALLATION DIRECTORY: /usr/local/rvm/gems/ruby-1.9.2-p290
  - RUBY EXECUTABLE: /usr/local/rvm/rubies/ruby-1.9.2-p290/bin/ruby
  - EXECUTABLE DIRECTORY: /usr/local/rvm/gems/ruby-1.9.2-p290/bin
  - RUBYGEMS PLATFORMS:
    - ruby
    - x86_64-linux
  - GEM PATHS:
     - /usr/local/rvm/gems/ruby-1.9.2-p290
     - /usr/local/rvm/gems/ruby-1.9.2-p290@global
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :benchmark => false
     - :backtrace => false
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - http://rubygems.org/
[deploy@staging01 current]$ bundle exec gem environment
RubyGems Environment:
  - RUBYGEMS VERSION: 1.8.21
  - RUBY VERSION: 1.9.2 (2011-07-09 patchlevel 290) [x86_64-linux]
  - INSTALLATION DIRECTORY: /usr/local/rvm/gems/ruby-1.9.2-p290/ruby/1.9.1
  - RUBY EXECUTABLE: /usr/local/rvm/rubies/ruby-1.9.2-p290/bin/ruby
  - EXECUTABLE DIRECTORY: /usr/local/rvm/gems/ruby-1.9.2-p290/ruby/1.9.1/bin
  - RUBYGEMS PLATFORMS:
    - ruby
    - x86_64-linux
  - GEM PATHS:
     - /usr/local/rvm/gems/ruby-1.9.2-p290/ruby/1.9.1
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :benchmark => false
     - :backtrace => false
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - http://rubygems.org/