gas charged are better all around.... do not use skyjacker stuff....shut up super stroked.....lol.... but the nitro will be better.... a quick explaination for you...
hydraulic shocks are cheaper to make so they are less expensive...they slow down axle movement up and down so its not a bouncy ride..i.e. ricers with cut springs going down the road...
nitrogen or just gas charged shock in general perform better in all scenarios as they do the same as a hydro shock when in the compression stroke, so its a nice smooth ride, but they are always trying to push the wheels down against the road so they give better traction and absorb the bumps quicker leaving less force reaching you in the cab....
If you can afford a gas/nitro charged shock, spend the extra money....they also tend to last longer too