Of course there OUGHT to be a difference....otherwise why spend the money? Whether the difference is "big" depends on what you want to do with the tractor and the thickness of your wallet. My budget and guess at how I would use the tractor led me to choose the TC 35. Though I have no experience with the larger engines on the same frame, I have yet to find a job that this tractor cannot do for me. I am doing lots of bush-hogging, pushing brush piles and trees. Pulling some stumps with a chain or lifting them with the toothbar on the 16LA FEL. Lots of hills. I am not pulling ground-engaging tools.
If I had more money to invest in this toy, I probably would have taken the "you can never have too much power" advice that you will find many places if you read this forum for a while. But I have absolutely no regrets about choosing the 35.
Good luck.
Chas