Seems like a rather odd comparison - although i pretty much had the same thought in mind.
If i'm not wrong, both should be as accurate - 0.1 cent accuracy for the boss and dt-10 i think.
However, do note that the DT-10 is a stomp tuner, and hence would compare quite differently from the tu12. As a stomp tuner, i think the DT-10 does the job pretty well, and seems quite sturdily built. In general, comparisons tend to be made between DT10 and the boss Tu-2, both being in the same league. In which, accuracy would lean more to the DT-10 (0.1) compared to the Tu-2 (0.3?) .
Personally, I own the Tu12, which i feel is a more versatile tuner since it is able to tune both electric guitars and acoustic guitars which do not have the electric (plug-in) capabilities. Also, you may find getting a reading off the TU-12 easier since it uses both a needle and rather large led arrows to indicate tunings. Also, the TU-12 allows you to alter tunings to certain freq, including concert pitch, which if i'm not wrong is not available on DT 10
If accuracy is really your pet peeve, then perhaps i might suggest you try the peterson Strobe VS2 Stomp Tuner, which offers accuracy up to 0.001 cent.
