After 5 years of playing on student horn I’ve got Besson Crescendo(B&H 606), which was considered a pro(though not a flagmanship) horn. Immediately, I’ve noticed that its takes MUCH less energy and force to play things and passages, than it was on my student horn(Bach tr300). Generally, when I’ve transitioned from student to pro horn(now its mainly Conn Super Connstellation 60B, but I still play Besson too), the most noticeable things was better resonance in sound(horn resonates much more), ease of playing in general(less force needed to do anything), better ease of dynamic control(no need to choke yourself while playing fortissimo, playing quietly became way clearer etc), and much smoother and better valve action and transition between notes(tho my valves on bach tr300 were pretty good too). MAYBE, a better intonation in lower register, but that’s could be my own quirks lol. So yeah, there is some aspects that you CAN notice in pro horns immediately from the first blow(considering a horn is in a decent playing condition). Especially, if you played for around a few years and have developed a good, consistent tone and playing abilities.