Q:

ORM vs parametrized queries if my only concern is speed of data access

I work in an ASP.net/ SQL Server development environment.  If my only concern is speed should I go with parametrized queries or should I use an ORM such as nHibernate or LINQ?

A:

Most ORMs support parameterized queries, so no difference in that regard. I would implement using an ORM as much as possible, and only optimize by handcrafting SQL when you need to. 
Understanding how the ORM works should help you build code that performs well. That way you can avoid obvious traps like calling a query repeatedly within a loop, e.g., when querying another table via foreign key.

A:

All things being equal, ORMs add overhead, so they start at a disadvantage.
On the other hand, an ORM might generate more efficient SQL than you and many of them come with built-in caching features that you don't have to write yourself (and if they suit your purposes, the improvements you gain from that caching might be greater than what you lose to additional overhead).

