The Zaphir chimes have a crystal clear sound, the Koshis chimes sound a bit more bell-like.
A Zaphir chime works good in wind-protected areas, as the plate where the wind touches is relatively big, the Koshis need a little more wind.
If you like it colorful, the obvious choice are the Zaphir chimes, the Koshis have a wooden natural look.
The Koshi set comes with 4 chimes, the Zaphir sets are available with 4 or 5 chimes.Zaphir 4 Set: Crystalide, Sunray, Twilight, Blue Moon Zaphir 5 Set: Crystalide, Sunray, Sufi, Twilight, Blue Moon
If you buy the Zaphir set consisting of 5 chimes you make the best deal, of course.
What about the tunes?
The tunes are quite similar. The difference is not as big as you might think, especially when you compare the Koshi Aqua to the Zaphir Sufi.
Here is the overview
Koshi Aqua: A D F G A D F A
Zaphir Sufi: F A D F A G A D (Intermediary Season)
Zaphir Blue Moon: D F A B C E A# C (Winter)
Koshi Aria: A C E A B C E B
Zaphir Sunray: G# B C# E G# E A C# (Summer)
Koshi Terra: G C E F G C E G
Zaphir Twilight: E G B C E G B C (Autumn)
Koshi Ignis: G B D G B D G A
Zaphir Crystalide: G A B D A G B D (Spring)