I would sell all. When a players cards are high like Dudas your best bet is to sell. If he were on a contending team then maybe hold. However with new york not going anywhere I would sell in a heartbeat. Just think what you can buy with $175 you would get for the blue elite.
A few players that I have noticed rising in price are
Mesoraco
D'arnuad
Bauer
G. Brown
Once spring training games start some prices may sky rocket. I am hoping a few guys I have invested in have really good springs.
It depends on what you have invested in him. If you paid a couple bucks for each auto sometime last year then maybe now is the time to sell some. However, take into consideration that the sterling is his only bowman auto and will be more desired than his elite auto.