The language mostly doesn't matter. There may be some benefits to some over others, but none are definitively better than all the others. The ML family language

The language mostly doesn't matter. There may be some benefits to some over others, but none are definitively better than all the others. The ML family languages with their rich type system and pattern matching can make some parts of interpreter/compiler building very straightforward, for instance, but they aren't the only languages with those features and other languages have comparable features or idioms. Some languages are going to force you to do more bookkeeping, like C, so you have to decide if it's worth the trouble for your circumstances. I'd recommend selecting a language you already know well, a language you also want to learn, or a language with libraries (or good bindings to libraries) that you want to take advantage of. If you want to make a compiler but don't want to do code generation (to machine code) yourself you may want to use a language with good LLVM bindings to get support for a lot of target platforms. If you're interested in making an interpreter, you may want to consider the libraries available to the host language. An interpreter implemented in Python gives you a chance to use Python libraries in your new language (same argument for other languages, the decision would be based on what libraries you might want to use).