Back when I was in my early 20's, before I buggered up my back and would split firewood every winter to keep the house warm, I special ordered a 25", 5 pound Ang Khola. I gave that Khukri the name Godzilla. He split wood about as well as a 3 pound Ax and Chopped 4" green Limbs in a single swipe. The Karda and Chakma were full sized tools, think Kumar Karda sized. The sheath, Khukri and tooks weighed in around 8 pounds! Not something that you want to wear on your belt.
Back before I sold him to a friend to pay college expenses, I used him to split lots of wood and chop and limb a few trees. It was impressive, though wearing ones self out was a distinct possibility. 2 years ago the friend I sold Godzilla to came over to Utah for a camp out and visit and brought Godzilla with him along with many other blades. Everyone on the campout had to test Godzilla out while doing some trail clearing, Even the girls gave him a try. We all had a blast. Holding a Custom large Khukri is something else and really cool! Seriously when ever I hold Godzilla I have a smile glued to my face.

I probably look goofy, but have so much fun using him in short bursts.
I've been using Khukri's to do most of my chopping for the last 11 years or so, so my experience level is pretty high. I was able to make quick work of 4 to 8 inch diameter dead fall. Much better time them most everyone else that tried Godzilla out. I noticed that Technique played a big part in how well people chopped with Godzilla. Some of the guys tried to use their impressive muscles to strong arm their way through the logs, others used fines and got through at the same speed but were less tired afterwards. My trick for using such a large tool is to bring gidzilla up to my shoulder, Start a swing, guiding him toward the target and let Godzilla go at his own pace. I'm just holding on and guiding him. Let the big blade do the work and hold on for the ride.
*Safety bit* Don't try to make any major course corrections with a large blade, it will more then likely end very badly for you. A 15" Khukri can take a persons hand or arm off, a 25" Khukri in the right hands can cut the same person in half shoulder to spine. Thats not a pleasant thought considering that Godzilla can probably slice a person in half on a ricochet. Always make sure that you know the target and the back drop. Big Khukris can blast through things faster then you think they will. Good swings are awesome, bad swings can be Very Bad!! Sure Godzilla is an Extreme case and a fun one, but it does help show what can happen if you are not careful. When you are tired, swinging a large heavy blade of any sort isn't good, more mistakes can happen and when things get big and heavy, little mistakes are now big ones. I'm not saying don't get a big Khukri, shoot, I practically started the Big Khukri movement here, All I'm saying is if you go the Big and Heavy route Be Carefull!!!
I recommend that people start in the 18-20" Range then move up from there if they want more. That way you have some experience with a Big chopper before moving on to the really big and heavy things. I started with a 15" Ang Khola (summer 2001) on the heavy side, then a 15" Sirupati and 16" Gelbu Special, WWII, M43 and then Godzilla. Sold some, bought some and ended up almost 2 years later (Spring 2003) with a 16.5" WWII and 20" Sirupati (still had the 15" AK and a 12" AK) which became my most used Khukris for many years. Right now my biggest chopper is an 18" ASTK thats on the thick and heavy side for an ASTK. It doesn't get used much, but if I know that I need to limb a tree thats the first one I grab. Honestly it's not the best chopping in it's size range that I've owned and used. The edge and edge shoulder are to thick. Thinning them out a bit will greatly improve it's chopping abilities. Right now it does okay, but below it's size and weight class. A thinner edge will help it bight deeper which in turn helps it cut out more wood per swing which is better. As for a battle blade, if I was Stronger in my arms, this ASTK would be unstoppable. The shear mass of it would allow it to smash through Old school shields and armor with ease. I'd pair it with a fast light blade for slashing and stabbing and use the ASTK to cleave helms, shields and armor. Smash the shield away the stab with the light fast blade. Mass, momentum and all that matter when bashing armor, not so much when chopping. Thin and fast can sometimes out chop thick and heavy.
The trick is finding a bigger Khukri that you can Carry and Use with out wearing your self out, that has good mass behind it and is still thin enough in the edge to penetrate deep into the wood. If it can't bite deep into the wood, all that mass is waisted, like in the case of my ASTK as it is today. Shoot, my 14 to 18" Machetes will out chop my ASTK and it's over 2 pounds (about 2.5 pounds?) vs a few oz for the Machetes. . . A proper Bone Cutter Khukri has the right combination of Mass and thin edge which enables it to chop really well! If I remember correctly it's do to the BC having a Thick spine, then it tapers quickly from there to the shoulder of the edge allowing the edge to be as thin or thick as it needs to be to bite deep yet still retain the strength for hard woods. . . . Godzilla had a 3/4" or thicker spine, but a thin edge, thats one of the reasons why it chopped so dang well.
Again, start medium sized which to me is around 18" and go from there. An 18" Ganga Ram, Bone cutter or maybe Ang Khola are what I would start with in Choppers. BTW a 12" Ang Khola makes a great small bowie knife. I use mine as a belt knife on trips paired with a pocket knife for smaller stuff and Khukri or Machete for the big stuff. A 12" Blunt WWII would also make a great belt knife to pair with your Bigger Chopper. And if you wanted something small more Bowie like, a 12" UBE or UF would be good, because they are essentially Clip point Khukris. . . Think of this last bit as a full service post. Covering what you asked about and something you might like.
Good luck with your search and Please let us know how it goes!