Question

In general, is one faster than the other, assuming 1 record is being returned?

Are there benefits to using one over the other?

Just as an example:

DataContext.TableBlah.FirstOrDefault(_blah => _blah.id == 1);

or

var test = (from blah in TableBlah
            where blah.id == 1
            select blah)

Answer 1

I’m 90% certain that

var test = dc.TableBlah.FirstOrDefault(_blah => _blah.id == 1);

sets up the exact same expression tree as

var test = (from blah in dc.TableBlah
            where blah.id == 1
            select blah).FirstOrDefault();

So your second example simply lacks the benefit of getting a single record by calling FirstOrDefault(). In terms of performance, they’ll be identical.

Personally, I would use SingleOrDefault() instead, since you’re looking for a single item. SingleOrDefault() will throw if you receive more than one record.