I have a small B series Kubota (B7610) and it has done everything I have ever asked of it and more. I have 40 acres, live on a hill with a 1,900' driveway. I have a farmi JL290 logging winch, 60" 4in1 bucket, 48" FEL Grapple, 60" rear blower, 6 1/2' FEL power angle snowplow, backhoe and a few other tools.
From time to time I wish I might have wished for a few more HP's but no more than 30HP. It is small and light enough that I can cross septic fields, and get in cloes to the house to use the 7 1/2' backhoe, But I have also enough power to do everything that I need to do.
It really comes down to what work you intend to do, and how you will use it. If you are using for a living, or working a farm, then bigger is definetly better. But if you are a homeowner who is going to plow/blow the driveway, do some landscaping, and haul some wood, then you don't need a great big unit.
If I had to do it over, I might trade up for a few more HP, but certainly not out of the frame size I am in.
Really try to go the the dealers and try out the different brands, as they all feel different.