What sort of riding do you an your mate wanna do? tooling around in the forest, Mr moto rides or MX and FMX. Whats he into as he will lead you in that direction.

A 250 4 stroke will do most things leaning towards MX ( ie Harrisville or Ardmore)
A Ktm200exc will do most things leaning towards enduro and woods riding
A yz or Cr 125 will be best at MX not so good at Sandpit or enduro/woods riding
A YZ or Cr250 will be best at MX but can be smoothed out for enduro or woods riding (Different gearing and/or fly wheel weight).
My pick for a bit of every type of riding after owning a Cr125, Cr250 and 3 x Ktm200's would be the 4 stroke 250 or Ktm200exc.
The 4 stroke would be good but my choice would be the 2 stroke everytime for maintenance and enjoyment. But each to their own.

But narrow the choices down after answering the first question.
Just my 2c