DPOS is still being developed so your question is good to see. Also, there are two avenues, one directly through JMT and your mobile device and the other through your web browser. The backbone of DPOS in both instances is
Justin whereas OPUS has two different programs running either OPUS-Rapid Static or OPUS Static. There are other factors employed in both OPUS and DPOS that the user needs to be aware such as DPOS will process GLONASS data when the IGS orbits are available and OPUS won't. Also, at present, the user cannot specify which CORS to use/exclude from its calculations in DPOS, but you can (and should) using OPUS. In brief, the answer to your question is you may see many differences for various reasons including those mentioned above. Frequently for my personal efforts in vetting OPUS and/or DPOS is to use third party software (Topcon Tools Demo) as well as a PPP service; e.g.,
CSRS PPP. Unlike all of the other methods mentioned, the PPP doesn't use vectors from other CORS and can even handle L1 alone through its modeling of the environmental factors in play.
The attached reports will give you some examples of the differences seen all predicated upon the same data file. Note the horizontal positions between OPUS and DPOS are less than 1cm, and that the differences in ellipsoid height are less than 2cm. In 8 out of 9 values, the PPP values fall between DPOS and OPUS.
ppp 9.330, .390, .542
opus 9.327, .393, .519
dpos 9.342, .389, .525