The dearer one looks almost the same as the one i bought off ebay , the cheaper one quotes 2 different batteries , i'd imagine you'd get the SLA batteries if you bought it , i've weighed my bike ( with SLA batteries ) and it's 40kg ( heavy ) , have a look at the links in this post
Derestrict via new controller?
Here's my bike i recently bought
electric mountain bike on eBay for £210 , it was a month old , also, Bikes, Cycling, Sporting Goods (end time 15-Jan-08 13:41:11 GMT)
Over all i'm happy with the bike , the batteries that came with it are a bit tired so i'm looking to replace them , but the size is not very common now , see my posts in the battery questions section , if you do decide to buy one of these bikes check every single nut and bolt for tightness and add some locktite to the rear wheel nuts as they come loose when riding .
atb
Wizard