Sanyo actually bought the battery manufacturing entity from Toshiba in 2001 and named it Sanyo Energy Twicell.
When Panasonic asborbed Sanyo, it was sold to FDK, a satellite company of Fujitsu, who renamed it to FDK Twicell (FDK has now been reabsorbed into Fujitsu as a division). It was sold as a going concern, so it's the same factory with the same technology and has continued to produce all Eneloops to date. It's now acting as a supplier to Panasonic, who apparently cancelled plans to expand their own manufacturing. Note that Panasonic did not sell the larger scale automotive battery line from Sanyo.
Non-retail cells are sold as FDK Twicell instead of Sanyo Twicell, it's just the retail cells that are branded either Sanyo or Panasonic (or both) or Fujitsu.
There are small differences between the cells, but you have to realize that this is more down to different generations or variants that co-exist. The last two Sanyo-branded models progressively reduced self-discharge and increased life expectancy. Technically, Panasonic's most recent model has marginally better life expectancy, but I wouldn't lose any sleep over it (2100 cycles vs 1800).
The higher capacity (2550mAh) cells have a higher level of self-discharge, but again, that improved with the more recent version to 85% retention after one year, vs 90% for the 2000mAh cells. The only drawback for most applications is cost and weight.
I would take claims of 3000mAh capacity with a grain of salt. That *might* be achievable under laboratory conditions, but in practise their effective runtime tends to be much less than with 2500mAh Eneloops.
