If I were you, I would prefer ActiveRecord, because I don't have to clutter my code with lots of SQL statements. Besides activerecord makes life easier.
Set it up like this
require 'active_record'
ActiveRecord::Base.establish_connection(
:adapter => "mysql2",
:host => "host",
:username=>"user",
:password=>"user",
:database => "your_db"
)
Then use tables like this
class SingularTableName < ActiveRecord::Base
has_many :table_relationship
end
Then query like this
SingularTableName.all #=> all records
SingularTableName.first #=> first record
SingularTableName.where("query")
SingularTableName.create("...) #=> create a record/row
You can find more methods here => http://api.rubyonrails.org/classes/ActiveRecord/Base.html
Update:
To overcome plural table names and default primary key, you can use
class AnyName < ActiveRecord::Base
self.table_name = 'your table name'
self.primary_key = 'your primary key'
...
end