The 3 valve compensating Besson/Boosey&Hawkes euphonium was often used as an intermediate instrument purchased by high schools here in the US during the late 1950s and 1960s as an alternative to the 3 and 4 valve American horns from Conn, King, Holton, etc. Instead of the upright configuration used exclusively in the UK, many of these horns had a rotatable bell forward configuration. While the 3 valve Besson had a superior sound in the hands of the right player to any American horns (3 or 4 valve), it was very awkward to march with. When using a lyre and "flip folders" that needed to be flipped with the left hand, it was almost impossible to hold the instrument with just the right hand since the horn did not have a "false tube" like the 4 valve horns, but instead just a thumb hook attached to the first valve. Also, when moving from parade rest or non-playing to actual playing the instrument, onbe had to flip the horn across the front of the body rather than just lift it like an American style horn. Most University/College bands started shifting to 4 valve euphoniums by the 1960s, so despite the wonderful playability of the 3 valve compensating Besson, they tended to be limited to secondary school usage. Universities like Ohio State continued to use silver plated American style bell front horns (3 valve I think) in the marching band for a long time (and may still today).
I played 4 valve Connstellations, 3 valve Bessons (upright and bell front), and 4 valve B&H Imperials from 1965 through 1974. My opinions above are based on quite a bit of experience.
Adams E3 0.60 Sterling bell - Prototype top sprung valves
Concord Band
Winchendon Winds
Townsend Military Band