Do you still have the buescher? I am lucky enough to have two horns, and old Martin and a new Yamaha. It is nice to have the contrast between the two. Sometimes I get frustrated with the ergos and the sticky pads on my Martin, and go back to the Yamaha. If I had to have one, it would be the Yamaha because of the reliability.
Sure, there is a very slight difference in the tone, but it can be compensated for.
I would stick with the Yani, they are super horns, and you don't see that many on ebay. I think generally they are "keepers"
In terms of tone production in my case it is 70% me, 15% Reed 10% Mouthpiece and 5% horn.
You may hear a difference when playing, but that can be to do with vibrations and perception. Try recording them back to back, you will be surprised at the very small differences you will hear.
The link below is for a tenor "shoot out" by Pete Thomas, but the principle is the same, it is worth spending time to listen to the clips. The differences are slight, and any one in isolation sounds great!
If the feel isn't right, most modern horns need tweaking, a good tech can adjust the action for you.
I tried a Yani A901 alongside my Yamaha, and thought it was superb, but too expensive in silver plate.