MV,
The EX-5 has a TON of potential going for it,
(killer sounds and massive real-time control)
but there are a few areas that need to be
'fixed' (sample loading times and sequencer
timing are the main shortcomings),but this
may or may not be a problem for you.
The E-synth, on the other hand is pretty much
all you could ask for in a single box, but at
about twice the price. It's sampler and sequencer are way better than the EX-5's
hands down, plus you have access to the tons
of samples from most major formats.
If price isn't a factor, you'll have way
fewer creative speedbumps with the E-synth.

B MAN

P.S. If your style is sample based, you may
want to check out Rolands SP-808 coupled w/
a cheap controller keyboard. You get tons of
sample time w/ all the FX you could ask for
plus a virtual analog synth, all for way
under $2000.