My 2002 911 Carrera Cabriolet needs a new battery. I took it to Eurotech in Livermore, Ca and they recommended a battery called World Source One. I've never heard of this battery and was wondering if anyone has this battery in their Porsche. Or, I'd appreciate a recommendation on a new battery. My old battery is an Interstate battery.

 

These are pretty good batteries. WSO claims they make exact-fit models for most cars and have a superior deep cycling capability. Not sure how good they are but they are quite serviceable.I had one as a replacement for a factory-bad unit in my '04 and no problems through 40 months of ownership: the dealer was replacing it at his expense so I felt I had no right to object.
When given the choice, I always go with a premium spiral gel battery (e.g., Optima, etc.) and I pick as the largest capacity that will fit in the space permitted. Usually I have to do a bit of measuring and reserach on line to determine what is the max capacity I can fit in, but I often get 10-25% more capacity that way. Many of my cars are modified (a harder to turn over to start) and the capacity comes in handy. Even with a stock car, like my Aston, with all the electronics, and on a cold morning when the car hasn't been started in a week, the extra capacity is good to have.