LLVM vs. GCC for iOS development
In latest iOS SDK, Apple provides three compiler options: GCC, LLVM with Clang and LLVM-GCC. I understand more or less what these 3 mean, what LLVM and Clang are, and so on. What I don't know is what this means in practice for iPhone developers. Which of these should I use at this point, as of January 2011? Is LLVM mature enough that I can use it safely without stumbling on bugs in it too often? Does switching to LLVM have any other disadvantages? If it does, then does the speed advantage outweigh them? Are there any other reasons to switch except speed?
Answer
Update: Because people are still finding this answer, I feel like I should provide a suitable update. By now, I hope it's clear that Clang is absolutely the way to go when programming, with Clang being the default compiler in the newer versions of Xcode and supporting ARC and new and upcoming language constructs (array and dictionary subscripting, literals, etc.). There's almost absolutely no reason to compile with GCC anymore, and for codebases using ARC and new features, using plain GCC is no longer relevant or possible (LLVM-GCC may support these features, but it provides no advantage over Clang now that Clang is completely stable).
By now (with LLVM-2.0 included in the Xcode 4.0 beta), LLVM is mature enough for production code use. It compiles a little quicker than GCC, and produces faster code, so use it whenever you can (pretty much, try to avoid GCC if something better is available). The standard Xcode 3.2.5 install contains LLVM-1.6 (not the latest), so I'd recommend either running some speed tests to see if there's a noticeable difference between GCC and LLVM, or compiling Clang from source and getting the latest version.
Essentially, there's no need for GCC any more, LLVM + Clang is more than enough.