I built my joiner's mallet when I was just getting started in woodworking. I hadn't seen too many mallets before then so I went with my gut instincts on size and dimensions. The result is a very hefty mallet made of hard maple and ash.
This mallet works well for me and I barely have to move it to drive a chisel. I've used it for long periods of time with minimal fatigue. But I have to ask, is there some advantage I'm missing out on that a smaller mallet has to offer?
I can't see the picture but I can just guess from .. That's quite the mallet! That size could cause some hardships....
If it is really big then you can have potential issues if you are trying to make delicate taps on a chisel or some other tool like a punch for small pieces. Sure, you could choke up but having a smaller mallet would be easier to handle I would say. If you are comfortable with the changes in force relative to the size of the tools and application then this might not be a concern.
I can't think of a scenario for this but it the mallet is large you might have trouble getting into smaller or awkward spaces.
Now that I have seen how big it is I could also see a problem with viewing your strikes. While you might not need to I would see the need to try and look around the mallet to see where I'm striking. That is mostly personal preference though.
There is no one telling you that you can't have more than one mallet! Build all the things.
Also, you say that you have used it for long periods of time with minimal fatigue. That could be subjective. I don't know what a long period of time is to you or how often you use it during that period. While this is not true for you, others might see the weight (Usually those mallets use dense wood) causing strain over time.
is there some advantage I'm missing out on that a smaller mallet has to offer?
As to big and heavy being actively detrimental I think that's a firm: it depends.
A physically smaller but still heavy striking implement (hammer, a lead-weighted mallet, or one made from lignum vitae or another heavyweight wood) could provide some benefits in some specific situations, purely as a matter of size and access.
There are plenty of purpose-made carver's mallets that are quite sizeable but generally these are scaled to the expected type of work, so big ones for large work and/or hogging off lots of material, regular-sized for pieces in a more 'normal' scale and smaller ones for working smaller or for use on miniature pieces.
momentum = mass * velocity
If you're hitting a framing chisel to hollow out a mortise in an oak beam, bigger is probably better. But the goal isn't always to hit the chisel as hard as possible. Given the equation above, you can see that you can achieve small amounts of momentum with a heavy mallet, but very small changes in velocity will produce relatively large changes in momentum because the mass of your mallet is so large.
If you need fine control over the energy you deliver to a chisel or gouge, a smaller mallet gives you more control within a given range by letting you use a wider range of velocities. The maximum momentum you can achieve with that smaller mallet will be less, of course, because there's a limit to how fast you can move the mallet. But the difference in velocities required to generate gentle taps compared to firm taps will be greater, which makes it easier to regulate.
It's the same reason that hammers come in sizes ranging from 6oz or less all the way up to a 20lb sledgehammer: different tools for different jobs. You could drive brads with a big sledgehammer, but you'd likely bend a number of them or hit your fingers because it's a lot harder to control than a small finishing hammer.
