What surprises me is that I see countless dog-flight posts, but effectively zero related to Angel Flight or similar. I did a few dog flights and then stopped as it really just seemed an incredibly inefficient way of helping animals (and the vast majority of the coordinators were completely useless). I now fly Angel Flights instead.
The standard Pilots'n'Paws flights I agree are typically very inefficient, but they're also usually filled by people who are looking for reasons to bore holes in the sky anyway, so it's doing something more productive than the $100 hamburger. We end up having $/dog being about equivalent to road transports because of the number we fit in the plane. The 414 is actually shaping up to be more efficient than the 310 on a $/dog basis due to its increased capacity, and it's more fuel efficient on the $/dog basis.
Of course, you can also argue whether the transports make sense at all vs. trying to focus on spay/neuter (this assumes you want to do anything to help animals, many people don't). Part of the goal of transports is also to get rid of puppy mills, so you have multiple objectives going on. Like with most issues, it is complex and there are multiple viewpoints. Obviously, transport is the one that I have latched onto as worthwhile in large part because it's an area where I can personally make a difference and it matches well with my capabilities and what I enjoy doing.
Likewise, Angel Flight (and the similar related organizations) is also a great cause. I've done one Angel Flight, but it doesn't fit as well into the kind of flying I like to do. Now with the 414, I do plan on getting a stretcher at some point and doing specialized missions that the standard Angel Flight organizations don't cater to, but that's a future state once we get the plane a bit more sorted out. Not that it's unsafe, but there are a number of details that I want to work on. Baffles, etc.
I respect the views of people who disagree with what I do (there are a lot of such folks who have told me everything from "That seems dumb" to "You have to be a ****ing idiot to do that," including to my face). My opinion is that any virtually charitable work you do is positive regardless of specifics or form. If nothing else, it creates more good will in the world, something that seems to be lacking these days.