DIS vs HIS-unanswered questions

[slymule]

Found a CVA Apex in 45-70 that I'm in the process of purchasing to have converted to SML. Trying to decide between Hankins' DIS and his HIS setup. Been reading posts for the last couple of weeks and watching a number of his videos, but cant seem to find answers to a couple of my questions. 1) Why does the DIS setup produce a higher velocity than HIS? 2)How many fps average increase in a bullet of 225-275 grains?
Seems to me if the velocity gain isn't substantial, that the HIS setup is quicker and simplier. Feel free to enlighten me if I'm missing something. Majority of my hunting is spot and stalk, no tree stands or blinds.

[BuckDoeHunter]

DIS has no bushing so more heat and pressure from the primer is reaching the powder charge. I believe Hankins uses a .080 flash hole in his DIS modules vs a .035 flash hole in the HIS plug with a bushing. IIRC, 100 fps more velocity is common between the DIS and HIS breech plugs.

[slymule]

Between reading a ton of posts and messages sent to me, I've definitely decided to go the direct ignition route. Any recommendations on who to use for this conversion and is there any difference or our all the gunsmiths using the same setup/materials?