Each of the items comes at a maximum power level of 270 — a base power of 265, plus a Legendary (purple) mod that raises the value by five. This scales to your player’s power level, so make sure you’re buying Xur exotics on your highest level character.
If you’re a Hunter, we can’t recommend Foetracer enough. It is arguably one of the best Crucible exotics in the game, letting you track players around corners and through walls after damaging them. For other classes, the gloves are OK, but you may have more fun with The Wardcliff Coil, which launches a wildly inaccurate volley of rockets.