Hello Izz
Do you want to work or play in your Unimog ? If it's work then maybe a short wheelbase with lots of equipment is the answer but you'll pay a premium for this.
If you want to play then the longer the wheelbase the more stable the Unimog offroad and the less equipment the cheaper she will be.
There is no easy way to discribe the model range only after many years one learns the differences and meanings roughly the first number denotes hp I've u900 87hp U800 74hp U1200 120ps U1400 140ps but this is not always the case as 1400euro 2 has 163ps or a u1600 can have 160/214/240ps many many options with hp !
Wheelbase again many many options normally 50 as in u1250 or 1450 or 2150 denotes long wheelbase then there is the options regarding extra long wheelbase like l38 denotes a wheelbase of 3.8m.
Interesting I was once told by a man at the factory that the L on the end of a Unimog like 1300L means it's a chassis for offroad not just denoting a long chassis, I'd like this confirming if anyone in the know can confirm this.
Happy hunting if you find something feel free to ask any questions.
Moose