I love the EX-5. I have owned Roland synths before and loved them too, but not the one you mentioned.
The sounds are great on the EX-5 and can be edited.
It does function as a sampler to althougH I have never used this function yet.
As you may have heard elsewhere, the workstation part is a bust, but you can always use midi to sequence the great sounds. It does have 64 bit polyphony