Here's my take.
disclaimer, I have owned and driven stage IIs, DD Jammer 4 edms and DD supermentals. Never owned Mach injectors (yet

)
I had a slight idle problem when the jammer 4s were in which is why I bought a used set of supermentals, but I really believe now that I have another problem, like my pump is failing. I have ruled out an injector issue (done this on the last 4 sets, only two of which were DD, one was custom set by an injection shop and the others were stock bosch). So I have another problem somewhere.
That said, the Jammer 4s were awesome. I sold them to a friend who removed stage III honed injectors and put these in. They were shimmed right on the money (within a couple of bar of each other). They run great in his truck but he has a new VP44. Very good low end power and much less smoke than you would think. After going to the jammers, he smoked his southbend Con FE with the TST on 9 so the low end is much better.
I have driven Mach 3s and 4s but have never owned them. They ran GREAT.
Remember when comparing mach 4s make 150hp and jammer 4s are rated at 125hp. I believe jammer 5s make 150 hp.
Between the supermentals and jammer 4s, the jammers had a lot more power down low. less smoke and about the same top end. But I like the supermentals a little more becuase my cruise control is more civil at 70 mph. The bigger edms had so much low end response that my 6 speed truck would "hammer" going down the road when cresting hills as the ecm tried to find the right fuel amount to match the desired speed.
I know some of this is off topic, but thought you might want to hear about it. Sorry for rambling on.
Jason