9 axis IMUs are improving all the time and the market is competitive, so all the latest ones are pretty similar, and usually, are well documented.
Pololu is a good source of boards with the latest versions, and unlike the junk on eBay, their boards come with I/O voltage translation, so they can be used with 5V processors.
"Accuracy" depends on what you want to do and the firmware or software. The latter has not changed much recently.