When the object leaves the ground it will have a certain KE = 0.5mv2. It will convert KE to PE as it climbs so some KE will be lost regardless of the angle.
If you ignore air resistance it does not matter which angle it takes. However air resistance is normally an issue. The space shuttle had to throttle back to reduce drag forces after take off. Once high enough it could accelerate again.
Jets prefer to fly as high as possible due to air resistance. They sometimes need to land and refuel if something prevents them climbing as high as planned.
The KE that you ascribe to an object depends upon the frame of reference in which you measure it (as does velocity). So, first you must be explicit about the frame of reference you are referring your measurements to.