Yes, you will get lots of opinions. Read into it what you will, but it is a true fact that Kubota has 60% of the market in that size. When you add in John Deere and New Holland, you now have 90% of that market spoken for. Also, according to published data, those percentages are not dropping.
My findings are that, contrary to what you may have been told, I've been able to buy tractors from each of the big three manufacturers for prices equal to, and in some cases less, than the lesser known brand tractors. When I've shopped for tractors, I've found that the lower volume brand dealers seem to want to make more profit per unit. So, in my particular area, that puts them equal to or higher than the so called "big three". I think it is because of this fact, the lesser known tractor dealers have actually been disappearing in my parts. Fortunately for buyers like me, the "big three" dealers in my area are still cut-throat against each other in pricing.
I'm very busy, and I also tend to trade tractors fairly often. My needs change, so I trade to get tractors that fit my current needs. I've found that in general, you have a much larger dealer support network for parts and repairs, and you have much greater resale value with the largest three makes. If 90% of the buyers are buying those brands, it simply gives a larger buying audience for them. That doesn't necessarily make their tractors superior in every way, and it is certainly still possible to have one of them break, but it does give them advantages.
I just have to think that it would be difficult to control 90% of the compact utility market, and maintain that percentage, if they aren't doing something right.