About MONO and Stereo samplin

Hi! Everyone. I am new in this game.
I would like to make sure about the mono and stereo samplin which one is better for instrument and other kits(not include drum and percussion).
I need choose one between EPS16+ and S3000.
I already have S950, I love the mono, I love mid 90s hip-hop sound(I think it almost mono sample in back ground).
I would like to make sure is the stereo sampler MUST HAVE?

Thanks for all of you help me.

There are no solid rules about this, but I have some general ideas:
- single instruments are almost always mono.
- when you play a real drum kit, each drum is an "instrument" itself, so it's almost always mono, but the positions of the drums in space means that the whole kit is a stereo* mix.
- when you create a mix, you're placing instruments in a stereo space, so that the mix is stereo. So, if you work with loops of mixed music, they arrive in stereo format (on CD etc.), because somebody mixed them that way.

These are only "general" ways of looking at it, but when you do it differently, remember that it's like an effect, because you're playing with the listener's expectations.
- putting a guitar through a chorus pedal is an example: it was mono, you're artificially making it stereo. e.g. The Beatles put vocals through a Leslie speaker to make them stereo on Lucy in the Sky with Diamonds and other tracks.
- so is playing a stereo loop in mono: it really changes the sound of the loop, you can lose whole instruments, depending on how it was mixed. e.g. the start of Eminem's Stan switches the same Dido loop from scratchy mono to stereo, for effect, and keeping it stereo made the song more radio-friendly (huge crossover hit).

So, I think you need a bit of stereo in there somewhere, it's a question of taste...

* you could replace "stereo" with "surround" if you have that facility

It's a matter of taste, and you can always pan your tracks after recording them to give some depth.
Basslines are best left in the middle, so there's no problem if you sample those in mono. Drums are fine in mono too, but hihats and cymbals work best panned slightly to the left or right.
Some instruments that have a lot of low as well as high tones (like a piano) sound better in stereo to me. I could be wrong though.