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Why select a BC547 over BC337 etc?

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I was having a look at the "Amplified Ear" project over at RED Free Circuit Designs - Audio (Amplified Ear - RED - Page38) and noticed that 3 of the 4 transistors were BC547 and only one was a BC337.

To this effect I have two questions:

1. AFAIK, the BC337 seems to be a better choice in every way over the BC547, so why did the author use the BC547 at all?

Would replacing the BC547 with BC337 in the circuit affect the system performance in anyway?

2. I would be using the circuit to drive a 32Ohm impedance headphone. This would mean a current of (1.5 - 0.7) / 32 = 25mA through the transistor at saturation and EVEN LESS when it is at active region.

In that case WHY DO I NEED to use the BC337 at all (BC337 seems to drive more current and have better hFE stability of 100 till 100mA compared to 547's hFE going rapidly below 200 at ~25mA)?

Would replacing the BC337 with BC547 in the circuit affect the system performance in anyway for such a scenario?
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