Which one should I buy? Note that one comes as a pair and hence the price difference.

http://www.amazon.com/Stamina-50-Pound-Versa-Bell-Adjustable-Dumbbell/dp/B000AMRN80/ref=sr_1_5?ie=UTF8&s=hpc&qid=1217222651&sr=8-5

http://www.amazon.com/1x50lb-Bayou-Adjustable-Dumbbell-adjustments/dp/B000MVKU98