I prefer the Perazzi.
If buying new and ordering the gun you can select the barrel lengths, rib style, barrel weight, chokes, mid ribs, bead type, trigger type, forend type, stock dimensions etc to suit your requirements. You don't have anything like those options with a DT10.
When ordering a Perazzi then, and comparing to a DT10, you can specify the gun with a stock to your own dimensions and barrels set up that it will handle like a DT10, faster than a DT10 or slower than a DT10 so to directly compare the fit and handling dynamics between the two is rather more complicated than it may appear at face value.
In terms of the actual design I like the Perazzi better, just me, and based on the new MX8's and MX2000's I have seen I believe the build quality is better than the DT10's as a rule. In my part of the world an MX8 or MX2000 is more expensive than a DT10 so it doesn't seem unreasonable to expect that the fit, finish etc might be a little better, you are paying more so you should get more and I believe you do.
If buying used or off the shelf buy the one that best suits you in terms of fit and balance or the one you shoot the best if you can shoot both.
The down side with the Perazzi options is that it means that looking at and shooting one Perazzi might not give you much idea about what some other seemingly similar Perazzi may be like. Two 32" O/U "Sporters" for example could be quite different guns depending on how they were specified and shooting one might not tell you much about the other. If one had 1500 gram fixed choked barrels and the other had 1700 gram choke tubed barrel they will be quite different handling. Stock dimensions on one gun might suit you down to the ground while another might be completely wrong. You might like the pistol grip on gun A while gun B might be very different (you can specify pistol grip dimensions). Gun A might have a flat tapered rib with only an orange front bead while gun B could have a parallel ramped rib with a white front bead and a mid bead. Etc etc etc ............
Bryce