What is the precision of intensity data in XRD measurement?
In short: what does the manual of your diffractometer claim?  Were you able to replicate its standards in first place?
The peak area depends both on the peak's height and width.  But this is difficult to answer because your question does not detail how data were recorded in first place.  Beside content (elements) and quality of your sample (remaining mechanical stress, orientation / size / shape of the crystallites, sample thickness), temperature and pressure while recording the data, the peak area will depend on the source (e.g., wavelength monochromators, slits widths on source and detector), type of detector, i.e. if a point detector was used moving around the sample, or a fixed image plate / area detector and data processing (e.g., how do you account for background intensity, (how) do you deconvolute peaks in question).

(modified from Stoe's IP-PSD)
If you opted for an area detector recording all intensities along $2\theta$ simultaneously, was it the same as for your reference sample?  You are set by the geometry and the inner design of this detector (pixel size and response to the radiation used) on $2\theta$-resolution and may improve intensity resolution only by change of the time of the exposure.
With a point detector, you are less limited for angular resolution because the detector may travel as far around the capillary or rotating dish as mechanics permit in tiny steps.  Large machines

(credit)
claim increments down to steps of 0.0001° (reference) which may equate to only one experiment per day but likely better peak resolution (think peak deconvolution), potentially with a much better signal/noise ratio than the area detector, especially if the sweep is recorded more than once.