There are many differences, but some of the things I like the most about Swift are:
- Safer type system, (e.g. no nil outside of Optionals)
- Mutability is discouraged, (but still possible if required)
- Type inference
- No headers
- Better support for concurrency
- Easier to learn & easier to maintain
- Much better support for the functional programming paradigm
- More powerful enum types
- Reference compiler is open-source and development is done in the open
- Playgrounds, (code is executed as you type is)
- Linux support