All import Estimas have the turbo diesel engine, which you cannot get in the UK at all. There are LOADS of gadgets available on the Jap ones, and if toys are your thing then you'll prolly want to look at a Jap one - examples are television, DVD players, tints, alloys, dual zone climate control, electric curtains, four wheel drive, etc etc.
There are two versions of body for the Estima (pre 2000) - one is slighlty narrower than the other (as Jap cars are taxed on internal volume) - the narrower one is the Estima Emina.
Only common problem on the diesel engine is blocked radiator, which can lead to a cracked head. The reason that there's so much room in the car is that the engine is under the floor pan, and mounted sideways.
My advice if you're after a good one is get one less than 10 years old, and it'll have to have an SVA test, which gives you greater assurances. I bought mine from a dealer, it came with a year's warranty, but it's been perfect.
Have a look at the owners club website for loads of useful info.
http://www.estimaownersclub.com
or feel free to yell.