You have somewhat conflicting requirements for "ideal" performance. With mowing, you want light weight. With a backhoe, you want weight and hydraulic flow. Heavy tractors compact the soil and/or leave ruts. If I were in your shoes, I'd get the biggest heaviest tractor I could afford and a zero-turn or inexpensive lawn tractor for the finish mowing. In the Kioti line, the CK35 is the one to get. The Kubota B's are nice too, especially the cab models.
I own a CK25 gear TLB (bigger than the 2510) and it's a beast for dirt work. I've had it almost 10 years now. But, I wouldn't mow with it. I mow 2 acres with a JD X739. In fact, I use the JD for most "yard" work, like aerating, dethatching, lawn cart, snow removal. But, when I want to dig or move piles of materials, the bigger CK25 is excellent. If you plan on moving any significant material, or do serious digging, you will be disappointed in the smaller machines. Notwithstanding weight, reach is king for backhoe work and the smaller tractors cannot accommodate a big backhoe. Loader breakout force is something else to consider, and if you ever want to load into a truck bed, look at dump height. With the QA buckets, you also give up some lift on the loader. Yet another reason to go as big as you can. If you go too small, your wife is right. You'll be looking to trade up.
You really should test drive the one's of interest. Your gut will tell which is best for you. Quality-wise, I don't see much difference between brands. Looking at my CK, it's hard to imagine where they could improve on quality. It's well made, end-to-end. And the CK line has been around long enough (around 2004 I think was first year) that it is now tried and true while making small improvements over the years.