The difficult tension for me is JVM vs. native. On the JVM I have Groovy, Scala, (Ceylon, Kotlin, JRuby, Jython, Clojure), even Java, which is an interesting milieu. Natively there is C, C++, D, Clay,Rust, Haskell which makes for fun tensions.
There is also Nimrod which has 'yield' and AST macros ...
