The DX7 is a fine synth especially if you run it through an outboard FX module for reverb, chorus etc. It has its own character and can't be beaten for certain digital sounds.

But if your friend needs acoustic instrument emulations such as acoustic piano, strings, sax, trumpet etc. then a Roland or Alesis is certainly a better option. Just as with analog synths, a digital synth like the DX7 is best at creating unreal synthetic sounds.

You just mention non-lead, but what sort of sort of sounds is he going to be using ? Pads, synths or electric pianos or what ?? That would make it easier to decide what sort of keyboard would be better for him.