mustang dyno vs. dyno jet?

just as the tag lines say's, what is the difference in nubers between the two? i had my 2007 v6 lay down 350rwhp and 355rwtq on a dyno jet. i just had it retuned on a mustang dyno and swapped software from the diablo sport to the sct. it laid down 325rwhp and 305rwtq. is this right? i feel that i have actually lost some power according to the numbers. i have not picked it up from the place yet but they told me that if it were on a dyno jet it would have put down about 375hp and comperable tq. is this true? i need help. i pick it up monday and i would like to know if they are full of it and gave me a weak tune, or are they correct and i will be very happy? please help, thanx guys.