Wow! Impressive! I've never written music, but I have performed and been in choir. Here's my take on each individually, for what it may be worth.
I think it sounds wonderful! The only thing that comes to mind is the 32 second piano introduction. To me, that's too long of a "not featured" instrument solo before the featured instrument(s) join. Oh, and it ends too soon. I think that's due to the size of the file, because it sounds like you continue beyond what is played in the clip.
I think this has real potential, and would love to hear the full score.
From a strictly music theory paradigm, I like it. The sound on the recording is too electric/digital to me. The sound reminded me of a midi sound (again, not the score per say, just the sound). It's a keyboard sounding tone (all three).
IMHO, the clarinet is a solo or featured instrument. I don't think it works well in multiples without accompaniment. Again, that's just my opinion.
Ditto the digi/midi sound. Horns are instruments that I think work well as a solo, featured, and multiples. I'd like to hear actual horns used to get the authentic horn sound. Theoretically, the score is cool!
The piano introduction is not as long, which is good (again, IMHO). At the same time, the end is all piano, but there may be more that didn't make it on the recording as it seems to end without resolution.
I think the flute isn't the right instrument for this duet, mainly because it is such a airy, "fragile", soothing sound versus some fairly assertive piano (Beethoven came to mind) arrangement. I really like the score on this. Of the four, this and the Bass Concerto are my favorites and IMHO have the best potential. I actually like the piano score on the flute piece more then the piano score on the bass piece. I think the respective scores for the bass and flute are equal.
Taking each as a whole as scored, I think the Bass Concerto is the best. It is closely followed by the Flute Concerto, with an idea offered of using an instrument other then the flute. Maybe even a stringed instrument? Or, having listened to it again, harpsichord (sp?)? I think it could work as dualing pianos, piano and harpsichord, or maybe dualing harpsichord (or two musicians using one instrument?).
The Horn/Brass Quintet stands at #3, mainly because of the digi/midi sound. I think the actual instruments would sound best. I recall as a youth we had a brass quartet in church, and it sounded great.
That leaves the Clarinet Trio, which I explained my thoughts previously. An excellent score in the making, but wrong instrument chosen IMHO.
Kudos to you and your efforts! Keep up the great work!