angski:
Battery
Almost every tool provider crows that they have 5Ah, 6Ah, 7Ah and 8Ah batteries. The bigger the batteries, the heavier the overall tool. Do you really want to carry 8Ah battery, climb up 2m up and drill a couple of holes, or would a 4Ah (which could be half the weight). Dewalt knew about this and recently, they came out with a lighter battery pack using mobile phone type batteries.
just keep in mind that a lot of tools perform a lot better on the bigger battery packs. the smaller packs tend to limit the output. something to watch when they come with 3ah battery packs.
also the "flat pack" battery packs can perform whole lot different. its best to check out the performance testing before buying.