"What should I buy" threads are always tough for me. I want to stay out of it, but I can't help having an opinion.
I'd buy the Mahindra over the Yanmar, more complicated machine or not. If you need that size tractor to do your jobs, that 3016 will do it better. Powershift transmissions are awesome compared to regular manual transmissions, but can't match the finesse of a hydrostatic in mowing or loader work.
The trouble is you say that the 1820D is appealing for its agility. Big tractors do the jobs little tractors do much faster, but little tractors can go places big tractors cannot. It doesn't take much dimensional increases to allow much better access: My YM186D will do things in many more places than my YM2000, even though it is only 1.1 inch narrower and 9.7 inches shorter. It's not even close, and looking at them it doesn't seem like they are anywhere near the same size on paper.
Another factor is that you have other machines available.
So, I would suggest you consider whether buying the 2310D or the Mahindra would complement the other machines available, or just duplicate their strengths. It sounds like the 1820D would clearly fill a desired niche that isn't currently covered by your family's tractor suite. It will pull a scraper or rake down your driveway, run a 4 to 5 foot mower, fit on a smallish trailer or tighter trailer, or whatever. Is that what you need?
If the 2310D or Mahindra are going to perform about like the TC33 does, in about the same size package, is that what you're wanting? Would you better served buying a skid steer, perhaps with a grapple, to do work in the woods and dirt? A skid steer will work dirt vastly better than a tractor of the same dimensions.
I'm not trying to talk you into or out of anything, but the mission drives the gear. I would try to make a list of things that are requirements, things that are ought-to-haves, and then things are would-be-nice-to-have.
Keep us in the loop, and take pictures of what you decide on purchasing!