French howitzers fired two types of ammunition. Cannister and shell. Cannister had a certain range [about 350m]. If you fired as shown in many of the books at high trajectory then there would be a difference between this and that of shell of 2-300m. However you could fire the howitzer over a flatter trajectory like a gun.
The Gribeauval 6.4in howitzer (3 calibres) was short and was more akin to a mortar. It had poor accuracy and precision due to this if fired at a flat trajectory. This piece was already obsolete by the 1805 and replaced by the far superior AnXI 5.92in [24-pdr] howitzer (7 calibres) which had a much longer barrel and was fired over a flatter trajectory. This was found to be more effective as the fragments from the shell had momentum in the forward diection rather than just from the bursting charge and gravety.
The Britsh could not elevate their howitzers above 12 degrees compared to over 30 degrees for the Gribeauval Howitzer. The higher the elevation, the great the strain upon the carriage. There are plenty of occurences of breaking carriages especially in sieges. Removal of the wheels and chocking up had been recommended by Dickson if I recall.