The limiting factor for accuracy for both of these sensors is drift rate and temperature performance. This stuff is specified in the data sheet- I pasted below, a little rough.
G_So% Sensitivity tolerance(3) at component level ±1 %
LA_SoDr Linear acceleration sensitivity change vs. temperature(4) from -40° to +85° ±0.01 %/°C
G_SoDr Angular rate sensitivity change vs. temperature(4) from -40° to +85° ±0.007 %/°C
LA_TyOff Linear acceleration zero-g level offset accuracy(5) ±10 mg
G_TyOff Angular rate zero-rate level(5) ±1 dps
LA_OffDr Linear acceleration zero-g level change vs. temperature(4) ±0.1 mg/ °C
G_OffDr Angular rate typical zero-rate level change vs. temperature(4) ±0.005 dps/°C
The _TyOff specs are pretty key especially if you integrate them to produce either angles or positions. Accel offset at 10mg means after 100 seconds- you could accumulate a speed error of 9.8 m/s of velocity which I think turns into nearly a kilometer of position error. You can likely get rid of 3/4 of this with software massagging but some of it is non linear like stiction and hysterisis. See if the vendor gives an guidance in app notes, etc. The gyro drift rate is worse really, you could be completely turned around (180 degress) in 180 seconds. Again, software or a compass can help here. Hope this helps.