A higher airspeed in the climb will give better forward visibility with the less nose-up attitude, and help keep the engine cooler. Vy will also get you to cruising altitude faster, reducing fuel burn.
While Vx might keep you marginally closer to the runway, it also gives you less margin of error when the engine does quit, therefore less time to get the nose down to resume glide speed. You might give up any advantage you had when you push over to regain that speed.
Use Vy, unless the airplane operating manual suggests something different.