I evaluated and reviewed the Optimate 3 only a few months ago in the warm and fondly remembered month of August (2008).
Wouldn't you know it -- just as soon as that review was published, Tecmate, the makers of the popular Optimate line of motorcycle battery chargers, released the Optimate 4.
I always figured a battery charger was a battery charger -- as long as it does the job, who cares? Although I will admit that some features are nice to have, like the microprocessors in the Optimate and other battery chargers like those made by Battery Tender, Acumen and others.
Their little brains monitor the battery and keep it maintained and topped off with a trickle charge in winter. To read the rest of the article: http://www.webbikeworld.com/r3/motorcycle-battery-charger/optimate-4/