Kay Humphries likes a good quality leather girth; also lampwick; the Stubben Trevira string girth; in cotton, the Aerborn type with stitching across the width of the girth rather than those with the centre stitching/tape, if you see what I mean.
You need to find a girth that spreads the pressure across its width rather than one that concentrates it in a narrow area. And of course all girths should be kept spotlessly clean.
Also try to avoid girths that make the horse sweaty if possible - not just because the sweat isn't good for the skin, but because they make the area slippy, which doesn't help if you've already got a problem with slippage.
Last one - if you use any sort of dressage girth it's very important to make sure it's long enough, so that the buckles don't interfere at all with the horse's elbow.