RE: Is 1 inch DIAMETER enough?
I cannot speak from a vast amount of experience with this issue though I was able to use one of the smaller cutting diameter heads on the market (Rocket Ultimate Steel) to take a nice doe this past season. I had no problem with the blood trail or recovering the deer. It is a fine little head in my opinion.
I have also recently had the chance to get a sample of the Sonic head you made reference to and plan on trying it out shortly. I do sincerely think that the new style of smaller, replacement blade broadheads provide an excellent alternative to some of the other choices out there.