What is the difference between the Duracell precharged rechargeables and the Rechargeable Accu?

There's actually a big difference, and what you choose will depend on your needs.

The Pre-Charged Duracell cells are what are called "LSD NiMH cells", or low self-discharge. While they have lower capacities (most around 2000 mAh for AA), they will hold a charge much longer when not used for extended periods of time.

The Non Pre-charged are "Standard NiMH cells". These will have higher capacities (up to 2700 mAh for some brands), but have higher self discharge rates when not in use.

So, simply stated, the pre-charged rechargeable will charge faster with each charge and will stay charged longer when not in use (for instance, if stored in a flashlight or similar). Uncharged rechargeables take longer to charge each time but will last longer with consistent use. However, if not used, will likely discharge after a month, so don't use those for flashlights you store in your closet. If you're going on a camping trip that weekend, they should be great or if you use them for your laptop or whatever, fine as well.

Example, I use my batteries for a Mac Magic Mouse, which needs basically consistent power and the uncharged ones should last longer (I actually want to say that so far, it seems like the pre-charged ones have been lasting longer, which contradicts this. NOTE: For the uncharged batteries, I have been using my 15-minute charger, which was made for the pre-charged batteries, over and over until I get a full charge, so my guess is a 24-hour charger would make a huge difference.

It's important, when purchasing the Duracell Pre-Charged cells, to make sure they have a white are a around the positive terminal of the cells, and are manufactured in Japan. These what some have termed "Duraloops", and are probably the best LSD NiMH cells currently on the market. Basically, they're Sanyo eneloop cells re-branded as Duracell pre-charged batteries. If there's a black area surrounding the positive terminals, chances are these are cheaper cells, made in China, that simply aren't as good as eneloop.

To get an idea of the self-discharge rates between the 2 cells:

eneloop LSD: Loses only 15% of it's charge when not used for up to a year.

Standard NiMH cells: Loses up to 100% capacity when not used over a period of a month.

Now, there are Standard NiMH cells that hold their charge better than others. The best I've found are the Powerex 2700 mAh NiMH cells.

Even with the higher capacity of the Standard NiMH cells, many times eneloop cells last longer in a device because they hold their voltage so well. So don't be surprised if you get as many or more shots using eneloop cells than you do using standard, higher capacity NiMH cells.