Honestly, the machines are so close you really can't go wrong with either of them. The Kubota 2660 has a little more power and the 2400 has two hydraulic pumps. I looked pretty heavily at the Kubota before I got my 2400 and the specs are "close". I was looking at the 2360 and not the 2660, but essentially they are the same tractor with a minor hp difference.
I could get the cub much cheaper (though, I'm told its going up in 2010) and the closest dealer (not where I bought from) for parts is closer than the kubota dealer. Here are some points I looked at when I was shopping around (cub cadet 2400 vs Kubota 2660)...
Engine HP: 24 vs 25.5
PTO HP: 16.5 vs 19
Hydraulic pump output: 7.2(double pump) vs 6.3 (single pump)
3pt lift capacity @ 24" behind: 661 vs 670
The loaders are real similar in spec as well:
Lift hieght at pins: 71" vs 71.3"
Lift capacity at pin, max hieght: 700 vs 745
Lift capacity at 500mm forward, max height: 550 vs 518
As you can see, it's a pretty close race. Double hydraulic pumps are a real nice to have feature. Though, the Kubota does have more power. I suppose that is the price you pay. The loaders are real similar in spec as well. What is odd is that the Kubota wins the capacity battle at the pins, but loses 500mm forward of the pins. So, I'd argue the loader on the cub is better engineered. Even so, they are so close in spec, it shouldn't sway you one way or the other.
I'd say, think about what is important to you. Try and drive them if you can. The newer BX Kubota "60 series" models apparently don't have the issue with the jittery start and stop as it pertains to the HST. I wasn't able to test drive a Kubota BX, but I've used my neighbors
B7610 and it's real nice. I wouldn't hesitate to purchase a Kubota. On the other hand, I actually purchased a Cub Cadet 2400. Really, it's my opinion (can't back it up) that cub cadet has nothing in these tractors and they are pretty much 100% Yanmar. My wifes uncle has a John Deere 2305 and, while similar, I like my 2400 better if for no other reason than the much shorter turning radius. Plus, I've always been an IH man and have trouble latching on to anything green
Good luck.