Becky,
its reasonably common practice,for irish fiddlers to play pickup notes with the main beat with one slur, I prefer a down, because from my own personal experience,I can get more oomph with a down.
One old irish fiddler i used to play with,gave me the example of the blackthorn stick[in g],and said to me,play the lead in note with a down sweep,with the next few notes.
of course its only one way of doing it,and people must do what they themselves prefer, there are[imo] no rules.
Guran,I find it marginally easier to get more emphasis when pushing.
but [imo]the important point is the reversal