Well, on the 250, I ran the Spartan first, just the 250 tune. I loved it, but it was my first diesel tuner. No shift on the fly was sorta weird, as compared to my buddy's cummins with bully dog... But, after driving mine, and then being in his, I was very pleased NOT to have shift on the fly, and beat his pants off of him..... When we did my first build, I wanted to do custom tunes on the Spartan, but it locked up, and would not let go of my truck.... would not load up the stock tune. Just a pain in the azz..... So, once we finally got it off, I was irritated with it, and sold it. The current owner loves it, and still jams the 275 as a DD. He is on here as well. I went with the mini maxx. Just the 300 HD tune. I tried KEM on it, and made less power, but was much cleaner than the 300HD. It was nice to have the shift on the fly, but it was sooooooo smoky, that I decided to try SCT with Erik's tunes. LOVED IT!!!!! But again, no shift on the fly. I kept the mini maxx for gauges, and future tuning options. SCT sucks balls for gauges......
on the 450, I used the SCT with Erik's tunes at first,(off of my 250 while she was under the knife again) and ran the mini maxx for gauges, then just the minimaxx (after I had to put the SCT back on the 250) It was ok, and smoke was much more under control with the addition of LOW BOOST FUELING adjust ability. I found a good deal on a Spartan, and gave her another shot. The Dash Daq, is a bad azz monitor. Hands down, the best that I have used. I am sold on the Spartan for the 450, and might try it again on the 250 at some point.... and I have already sold my mini maxx.
for me, the setups that i have found that worked best, on the 250 is SCT with Edge CTS for gauges. and on the 450, Spartan for all purposes.
Not gonna bash anyone's tuning, or toss out HP #s, just what works best for me. If H&S gets other people to do custom tuning, I think it would be a viable option, but I will continue to live without shift on the fly.... SCT has awesome trans control options. Spartan has pretty damn good trans tuning, and I really did not like the H&S trans tuning.
Basically, shift on the fly is the major difference. Everything else is user preference.