congratulations. what music do you enjoy most at the piano ?
if the three instruments were of similar age and condition, my guess the boesendorfer was the most expensive, the feurich most reasonable. 1990 was just ahead of bechstein purchasing feurich, and from that date forward there was sufficient turmoil and uncertainty around the company (bechstein did not remain owners for very long, then the name feurich was used by two different concerns in different cities, with the vienna branch giving rights to a chinese maker Hailun at one point) that a buyer must exercise extreme care and caution to distinguish the pianos made in Langlau, like yours, from the others. prior to 1939 the company was in Leipzig and established itself as one of the top deutsche piano companies.
have experience only with the mason and hamlin of the three you considered ; we were fortunate to find a 1919 BB in restorable condition. m&h had its own ups and downs after aeolian took over in 1929, with good pianos persisting while they remained in Boston in the 30s, diminishing and depressing decline as time went on with factory relocations and ownership shuffles. the company was reborn in 1990 with significant recapitalization, revival of the original designs, and establishing manufacture in Haverhill, Ma not far from its origin. the original designs have features more in common in european pianos vs. new world or asian designs, and of course the unique tension resonator in the grands. a BB made in the early-mid 90s was in the generation when m&h reestablished itself as a first tier maker.
was there something that appealed to you in the three pianos you liked that you did not feel and hear in comparable Steinway pianos ? just curious, because the comparison between s&s and other top makers gets brought up frequently.