When comparing Scala vs twinBASIC, the Slant community recommends twinBASIC for most people. In the question“What are the best general-purpose programming languages?” twinBASIC is ranked 12th while Scala is ranked 27th. The most important reason people chose twinBASIC is:
Any code that runs in VB6 will run in twinBASIC (once v1 is released). Code that runs in VBA will also run in twinBASIC, though you need to account for any dependencies on the host application's object model (e.g., the Excel or Access Application object).
Specs
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Pros

Pro Immutable values
The immutable values make it perfect for working with concurrency
Pro Multiparadigm
Scala supports both Functional and Object Oriented styles of programming. Beginners can learn both paradigms without having to learn a new language, and experts can switch between the two according to what best suits their needs at the time.
Pro Type inference
Scala offers type inference, which, while giving the same safety as Java's type system, allows programmers to focus on the code itself, rather than on updating type annotations.
Pro Compiles to JVM bytecode
Aside from Java itself, Scala is by far the most popular of the many JVM languages. If you're developing for Android, or a similar JVM-only platform, or otherwise need out-of-the-box cross-platform compatibility, but the performance of a compiled language, Scala is the way to go.
Pro Very good online courses
On coursera you can find great introduction to Scala by Martin Odersky.
Pro Type inference leads to a simpler syntax
Pro Expressive functional programming abstraction for reusable and safe code
Pro 100% Backward Compatible with VB6/VBA
Any code that runs in VB6 will run in twinBASIC (once v1 is released). Code that runs in VBA will also run in twinBASIC, though you need to account for any dependencies on the host application's object model (e.g., the Excel or Access Application object).
Pro No runtime requirement
The lack of a runtime dependency makes twinBASIC applications very lightweight and portable. Additionally, compiled executables only include necessary code from any referenced libraries. The classic "Hello, World" program compiles down to an 8 KB .exe with no external dependencies.
Pro Compile DLLs to extend VBA functionality
Can be used to extend VBA functionality by compiling standard and ActiveX DLLs in both 32 and 64bit.
Pro 64bit compilation is supported
64bit compilation is supported, as well as 32bit.
Pro At last! a replacement for VB6
At last there is a replacement for Microsoft VB6 - and for VBA too - twinBASIC programming.
Cons

Con Can be intimidating for beginners
Scala is an industrial language. It brings functional programming to the JVM, but not with a "start small and grow the language" perspective, but rather a very powerful language for professional programmers.
Con Way too complex for beginners
Even for seasoned programmers it's a difficult language.
Con Static type system inherits cruft from Java
The type system is too complicated yet still less powerful than Haskell's.
