Given that 1.9.3.dev is effectively an “immature” 1.9.3 RC, I would say, yes, it will have a similar performance. However, I would not go using 1.9.3 at this stage as it has not yet been officially released.
Though what Ryan Bigg has said is true, Ruby 1.9.3 is and will stay faster mainly due to the load.c performance patch. Here are a couple articles explaining that:
http://www.rubyinside.com/ruby-1-9-3-preview-1-released-5229.html http://www.rubyinside.com/ruby-1-9-3-faster-loading-times-require-4927.html
