There are two Kosher Butcher shops in my neighborhood. Both are certified by the local Council of Orthodox Rabbis with a Kashruth superviser that comes and goes (Yotzee Venichnass). However, one is owned by a Shomer Shabbat and the other by a non-Shomer Shabbat. As an Orthodox Jew is one shop preferable over the other?
It is important to support a fellow Jew. It is even more important to support Jews who are Shomer Shabbat – you have a share in his mitzvah if you support him to be able to perform that Mitzva. However that does not mean that you always buy from the Frum Bucher, more factors should be considered like – is he poor? Is supporting him may bring him closer to his Yiddishkite? Is the Frum Bucher a decent honest man? And so on. To get the best answer you are better off asking the Rabbi of your neighborhood who knows the people involved. Kol Tov