Ruby is slower than PHP and Python. Guile Scheme compiles to native binary OR can be interpreted, and doesn't have a global interpreter lock. At least python gives you better threading options than ruby.
These ruby quotes and this encyclopedic page explain it best. Rails and the ruby community is a ghetto. Ruby developers tend to be textmate and mac loving hipsters who cling to brand and celebrity with a disgusting zeal. They also tend to latch on and circlejerk fads like Agile which plague the programming community with continuous non-substantive articles. Rubyconf is a circlejerk of the slowest OOP frameworks in the world coming together in one spot and competing over which framework uses the most frameworks for higher webscaledness. Among the "best" in the community, OOP and classes are (mis)used for everything even for simple things that don't require hierarchical structure. Guile scheme developers on the other hand are the type of people that take on languages even if they aren't popular and hyped. They're curious people who were not sold the idea of language at some noisy ego conference. Guile scheme implemented OOP as "GOOPS" after taking ideas from CLOS and the art of the metaobject protocol, which Alan Kay called "the best book written in ten years".
Guile scheme has better C integration than lua. If you need performance for the performance critical parts of your application guile scheme has you covered. Guile scheme can also complement any language that has C integration. What about ruby's nifty features and language syntactic sugar? Guile scheme has a macro system that's nearly as good as lisp. Want a specific language control flow feature? Simply add it with a macro and it gets translated at compile time.