Practice is not a factor in this case. Some instruments are indeed inherently faster than others, and the reasons are varied. In the case of the extremes of the bugle family the column of air to be set in motion for each note is massively longer in a bass tuba than in a soprano cornet. But even between instruments of comparable pitch there can be differences that render some be faster than others. It takes less physical movement and energy to progress from one note to another on a euphonium than on a slide trombone (the only possible excuse for development of the valve trombone). Likewise, on balance, on a cello. There are of course several other ways in which the differences between instruments affect the inherent playing characterstics.