So, you ask an impossible questions; a simple This One is Best.
So, let's try to have a couple key features that we judge; and I'm assuming commercial use, not weekend warrior/diy/homeowners
1) Parts availability/support
2) Reliability, that's actually going to be hard to judge,
3) Hydralic flow
4) Pushing power
5) Operators station
6) Novel features/stuff only available on a few
7) Total expected ownership cost for 2000 hours
If we have CAT, Deere, Case, Kubota, Bobcat, JCB, Takekuchyi, Gehl, Kioti, Komatsu, Terex, New Holland, Wacker Neuson, Volvo, and I'm not sure is Sany, Ditch Witch, Vermeer, or some others have a CTL. You also have Possitrac that I thought got purchased, but I'm not sure on that, and if that affects anything
So parts support (by that i also mean Speed), Cat is definitely best, but you also need to consider what is close to you. If your in the UK, maybe Volvo and JCB are faster to get parts. If your in Alaska or Texas, it might be different. If you already have to go to the Deere dealer several times per week, maybe a Deere is best for you.
Reliable; I'm not sure if want to pick one, it depends on a combination on information the company won't share, your specific use if the machine, ect. What might be most reliable in a mulching environment, might not be the best in dirt, or rock, or an loading role.
Hydralic Flow; the CAT high flow machines are towards the top, ASV's largest do have excellent flow, and you can't compare a low flow Kubuta model vs a High flow deere. or vice versa
Push Power; That kinda depends not only on the weight/HP, but also the design of the tracks, and all, the larger ASV are undoubtedly able to Push an amazing amount, but I can't say for sure it's the most
Operators station, some of this is 100% preferences, up vs out doors, (if going enclosed), how your arms rest, how tall you are, ect. If you are running something like TopCon, how/where you place the screen, all that,
Novel Features; JCB Robot has some things that just aren't available anywhere else; they have "teleskid", side entry door, ect. Case, i have seen some of their bigger CTLs with steel tracks. I dont mean track overs, I mean purpose built, CTL, with steel, tracks. I believe they are non-cleated, basically track hoe (or HDD) steel tracks
Total Ownership cost; I'm not going to do that, but You should. Figure purchase (or lease, or lease to purchase) costs, known maintenance (tracks, rollers, filters, fluids, ect) for a fixed period, With the options you want