I have Del's 5.25 and 6 inch senko molds. They are both hand pours and I will never part with either of them. I have poured many baits with them and have caught many fish with them. They are great molds.
I also have several Bass Tackle 5.25 stick molds all of which are injection. They are a little thinner than a senko, but still make a great looking bait. They are much easier to pour than Del's hand pour molds. I have caught many fish with them as well.
I think I also have every carrot mold ever made. They are very different in appearance than a senko, but much easier to pour. And you know what, I've caught a lot of fish on carrots too.
I compare your question, Jay, to the old argument of what's best...Coke or Pepsi? It all boils down to personal preference. Fish are pretty fickle creatures and often times we don't know one day to the next what they're going to bite. So there is some validity in having one of everything.
For me, injection makes a whole lot of sense over hand pour. Size does matter, sometimes, but not always. So, what's best? Diet Coke, of course.