a 150mm for 4x5 is more than adequate. 210mm would require a much longer extension on the enlarger column (think vibration). Additionally, the bellows would probably not be long enough and you'd have to find a lens cone. All to be avoided.

I seem to remember that the APO Geronar is pretty bad, with lots of light falloff in the corners. (anyone who knows better, please correct me.)

I think your best bet is to find a used Componon or Componon-S (newer) 150mm.