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NiMH Batteries on Picaxe 28x1, 2500 2700 or 2900 mAh

I've been doing some research about batteries and I've stumbled upon Rechargeable batteries that come in 2500 2700 and 2900 mAh. Obviously they are 1.2 volts and I am looking to use 4 of them to power the micocontroller at 4.8 but I was wondering if one was better than the other . . . After some NiMH research I came across these batteries at www.vapextech.co.uk (2900mAh) and was wondering if 2900 would be the best way to go.