Good question
I have never tried the 370's. I had bought a set on a GP and I sold them. Joe D tried the Diesel Dynamics injectors, and really liked them. It was a tough call on which way to go.
Price wise, they are about the same.
This is what I know:
Keith @ DD says their Stage III's make 8 hp less than a 370. He also went on to says they smoke less, idle better and are 10 times more streetable. ( a sales pitch, but it seems true).
Ted Jennety has the DD stage III's listed at his web page at an 80 HP increase. What the baseline injector they compare it too , I'm not sure.
This is what Joe D ( the Godfather of 12 Valve performance) said about the DD III's vs. 370's:
"I feel that the extra quality control and hand labor DD lavishes on his injectors result in a very fine product. Stock Bosch are very good, but as with any mass produced item, there is more possibility of variation in quality. I cannot estimate closely how likely it is that someone would get a less-than-ideal injector from Bosch. I would think the chances are rather small, but I know DD discards a fair number of new Bosch parts that don't meet his quality or performance standards.
Regarding DD3s vs. 370 Bosch for the 12 valve engine, both make a lot of hp and torque. Either of these injectors is close to the limit in power you can get from extra fueling while other engine components remain stock or lightly modified. The Bosch 370s have a fuel sac in the tip and that makes them richer at idle and low power conditions than the DD3s which do not. I anticipate that the DD3s would give somewhat better mpg especially in town driving. However, the DD3s cost more, due to the handwork and quality control procedures, and to their insistence that only the very best get boxed up for sale.
Note that my tests involve the 370 injectors that Piers and I worked up, and only some of the vendors offer that part number while others use another part as their 370 injectors. I cannot address these other injectors' performance characteristics as I haven't tried them.
I might also comment that a portion of the added value of DD injectors comes from their proprietary modification processes, procedures, and methods. Part comes from quality control, and part comes from use of only the best of new critical parts. Only recently did I investigate DD injectors as an alternative to Bosch, the standard we go by because it is OEM [original equipment manufacturer] in our Rams.
Here is an example that shows why I feel DD is not just a welcome exception to the run-of-the-mill or generic aftermarket or rebuilt injector, but also that DD gives us a new standard of quality. A Rammer whom I know recently dyno tested DD Stage 2 injectors against another vendor's Level 3 product at a third-party dyno installation. These tests were conducted at approximately 5000 ft. altitude. The "low-cost" injectors [not really much cheaper since we are comparing DD2 to those 3s] gave 303 hp and LOTS of smoke. The Stage 2 from DD gave 329 hp and very little smoke. I know from experience that DD Stage 3s would give even a bigger hp difference and still very little smoke.
Thus, it's worthwhile to shop carefully for best value, not just lowest price. "
Attention: TDR Forum Junkies 
I don't blame ya Todd, I wouldn't want to pull my injectors AGAIN either, maybe in a few weeks. 
