Space required and design desire are the two main considerations.

A pocket door requires less space and can fit in most design areas.

A slider needs more room(double the width of the door) and only fits a couple design areas, IMHO.

Thanks handymac - so it looks like there is no difference in the hardware required? my workman was telling me the pocketdoor is "more expensive" sliding door is cheaper or some such thing - if cheaper is quality compromised, was what I was wondering...
Our workspace is for a single door, and the rest will be hidden in the pocket - which is currently an open wall..

The large difference is in where the door goes when open.

A sliding door usually overlaps another door.

A pocket door slides into a pocket in a wall.

Both require framing twice the opening width, though with a pocket there are ways to make the pocket portion in the wall not require a header (turn the studs 90 degrees and make the wall thicker).

Sliders almost always use a floor mounted track for the door to ride on, pockets can hang from a track (though they have been on floor tracks and even more complicated mechanisms in the past).

greenfingernail-
I think you need to get your handyman to be more specific about what he means by these terms. Somewhat different hardware is required for the two and he should be able to show you exactly what each would entail, and why the costs are different. In addition, there is also the concept of the residential "barn door" style, which is a door that slides back and forth on a track that is mounted on the outside of the wall. He may or may not be talking about this when he refers to "sliding doors."

Here is a link that might be useful: Barn Door styles

thanks kudzu - i will ask him; either way, I do want a sturdy solution not something that will slide off the rails every other month - I plan to seal off the wall into which it is going to slide; then it would be a lot of trouble to get stuff back on the rails; the barn door styles look good but seems to be for heavy duty uses; also found johnson's hardware - my handyman may be buying something locally; let's see what he says..

It all come down to cost and what you would like. The doors you select can be used in either a slider or a pocket door so the cost of the door is not an issue it is the cost of the labor thats what you need to get from your installer.