I heartily recommend nREPL.el for various reasons:
swank-clojure is dead officially, but has been dead for a long while. While it was getting some job done, nothing much has changed or improved in it after its initial inception. The development of swank-clojure required significant expertise in Common Lisp, which Clojure developers generally lack and are unwilling to attain.
clojure-mode 2.0.0 doesn't support swank-clojure + SLIME at all. This move was hugely beneficial to both clojure-mode (which dropped a lot of legacy code) and nrepl.el (which's development pace was increased after the announcement).
nrepl.el is picking up features really FAST. I'm one of its contributors so I should know :-) Recently a lot of cool things like macroexpansion, compilation error highlighting and multiple connections support were added, just to name a few. Many more features and refinements are in the pipeline. nrepl.el's architecture is much simpler than SLIME's and it's much easier for regular Clojure hackers to extend nrepl.el.
SLIME syntax highlighting? The REPL has the same font-locking in both SLIME and nrepl.el and the source buffers are using clojure-mode's font locking. It other words - syntax highlighting's the same in both.
Emacs Live relies on vendorized git submodules and generally the versions of the extensions it ships are lagging behind the upstream a bit. You might want to try as an alternative Emacs Prelude, which also ships with Clojure support, but always uses the latest packages available in MELPA.
There is no slime-repl
(outside SLIME that is). At this point it's just swank-clojure + SLIME or nrepl.el. Given that nrepl.el even now implements most of what SLIME has - you'd better get used to using nrepl.el.
Update
nREPL.el was renamed to CIDER after version 0.2.0.