Are there any DISADVANTAGES in a OHC design engine vs. pushrod type?

I own both types--a 4.5 SOHC Mercedes, and a 455 Trans Am.

I always assumed the OHC design was a better design in every respect. So I was suprised to hear someone say the pushrod type offers the advantage of a flatter HP/tourque curve over the full RPM range. Is this true? Are there any other comparisons that favor either motor?

Thanks