I've used Sonicare since 1996. The AA have the same power but no 'quad' pacer nor the ills of NiCd technology in the rechargeable, not sure what battery chemistry is used today. Many complaints about water damage are due to failure to care for the o-ring to insure a water tight seal. I have 3 Xtremes of my own, and I gave away another 4 as gifts, after showing them how to clean the battery cover all are alive and well since 2008.
With removable battery units you can insure the battery is in top shape, and easy to replace DIY. With alkaline I get ~ 3-4months, and NiMH ~ 2-3 months per charge. I have two in service until the battery dies, when it does I switch to a fresh handle, so I don't get my brushing interrupted. After brushing I service the dead handle and put in a fresh set of batteries, which is then put in the backup bin. The other handle is also in use but the battery is offset by 2- weeks so both in-use handles never die simultaneously, and there is always a backup ready to be used.
When I bought them they were maligned because of the leak issue, I got them between $12-15 each, nearly the cost of a replacement brush.