A lot of people like DHT and they are a sponsor on this forum, But if you research DHT on this forum, you will see a lot of people have issues with them. DHT always seems to stand behind there product, but they do seem to have a lot of issues with them compared to other brands.
As far tonnage rating's it all boils down to how much wood are you ganna split. What types of wood and how fast do you wanna do it.
If budget allows, bigger is always better. Panoto is correct that you just can't throw wood on any splitter, willy nilly and expect it to work.
I bought the Countyline 40 ton unit over DHT because of two things. DHT seems to have a lot of issues and the countyline is heavier built. It has a bigger pump, motor, hydraulic hoses and fittings, bigger cylinder, taller wedge, bigger tires, bigger oil tank, better fold down leg support, faster cycle times. I use my splitter almost every day and didn't want to be broken down waiting on parts from the manufacture. Ok more then 2 reasons. I have put 110 hours since I bought it in Jan this year and it is a very good unit. I really like it. I have been splitting 50+ cords a year for over 15 years so I have a lot of time on a splitter.