For just about any disc drive manufacturer you can name, some people will swear by them, and some people will swear at them. I think they've all been guilty of producing an unreliable series at sometime or another. Or they've pushed slighly too much from one generation before introducing the next, which leads to problems with particular sizes while the rest are trouble free. You should also note that several makes have now merged, such as Maxtor and Quantum, so the same drives may be sold under different trademarks.
I'll have to disable the fan in the caddy to compare the spinning noise level of the Maxtor DiamondMax in the Iyonix and the Segate Barracuda backup drives. The latter are certainly quieter when head stepping, and have faster seek times (a DiscKnight check takes half as long), but the overall transfer rates at various block sizes (using PowerTec's !Speed) are almost identical.