fkach,

Not too many Derby winners have run a race as good as their Derby win prior to the big race. It’s certainly an unfair standard as to whether a horse belongs in the race. The 2 main BG contenders, Hard Spun and Street Sense and perhaps Great Hunter, have definitely shown they have the ability to at least be competitive.
Yes, I believe that Poly a offers a safer choice for a prospective TC contender, but my feelings for the surface doesn’t influence my advice that the owner of a horse who’s dirt form is marginal should establish dirt form before going into the Derby.
In the cases of SS and HS, who have already demonstrated their ability, barring some injury, a final prep on the synthetic surface is a wise choice. The fact that they have also shown ability for both surfaces, especially HS, is an added plus.

Bob