The original is mechanically and electrically better -Kurzbericht- Sigma BP-41 Li-Ion battery

1) mechanism: The geometrical dimensions and the materials used allow easy replacement, where you have the camera "do not shake". The battery can be easily removed. Since the battery flap a DP-2 Merill stays longer heal.
2.) Electrical: Much higher capacity, which is very favorable for the consumption. Lower capacity rather annoying.
3.) Electrical: contact with high gold plating, therefore not expected to contact problems. You want the battery so use a long time reliable. Compared with lower-priced variants the higher gold plating with the naked eye is already visually recognizable,

Conclusion: Despite the high price is a worthwhile investment! Uwe Zenke