The Arcane Connection is for long distance attacks, troubles. sure it gets them inside their Aegius, but Demons will have a hard time breaking through the Aegis anyways.
What you typically have (and I have this in spades), is Magi who pump their Parma score after the first encounter with a magical threat.
So even if you get an Arcane Connection you (the demon/SG) cant penetrate their magical defenses.
Which is why I think Sympathetic Connections are more important. THEY are what allow you to penetrate their magic defenses.
If your a (SG) Demon and you decide to stalk Maximanus of Tytalus... and he is currently holed up in his Lab reading some boring book and not out side playing "guess the sin" with you... you attack his connections, his allies, his sources of power OUTSIDE the Covenant... then when he comes out you have him in your sights. As a young boy, black cat, or turkey vulture (he cant see through your illusions!) you stalk him, and bedevil him with your sympathetic connection through the Sin of Wrath, which allows you to push through his Parma of 3*5 + Form Score. Most Demons will need to be two to three magnitudes higher than their Targets Parma to penetrate ... and that can lead to some big demons walking around with nothing better to do than pull prnaks on Magi. Where a x3 Sympathetic Connection and a moderate Penetration Score (all the better to bedevil other Demons of course), moderately powered demons can be a challenge to both Mundanes and Magi alike.
Of course Virtuous Magi have nothing to fear!
Sympathetic Connection Multiply Adders by the numbers:
Note: Recently means since last Confession/Communion
+3 Recently committed a Mortal Sin http://en.wikipedia.org/wiki/Mortal_sin
+2 Recently committed a Venial Sin http://en.wikipedia.org/wiki/Venial_sin
+2 Committed a Moral Sin, but has since had Communion, but no Confession
+1 Committed a Venial Sin, but has since had Communion, but no Confession.
+Y Where Y is the value of a Personality Trait that Maps to a Cardinal Sin (Lazy, Angry, Jealous) http://en.wikipedia.org/wiki/Cardinal_sin Only Applicable is the Demon has an Obsession Power related to the Cardinal Sin.
Confession permanently removes the Mortal and Venial Sin Bonuses
Communion temporarily removes all Sin (Mortal, Venial, Cardinal) bonuses but only lasts for a week, and unless the Sins are Confessed they should return.
So a Magi who recently Killed another in Wizards War and is Jealous of Others +2 might be very vulnerable to a Minor Demon of 15 power who had no Penetration Ability ... His normal power level would likely not get through a Parma of 3 since even with a 1 pt cost the Penetration would be 10. With the Murder and the +2 Modifier the Demon would have a x 6 Penetration Modifiers (1 base + 2 Jealous + 3 Murder).
Confession would bring that to a x 3 (Jealous + Base)
Communion would protect him and bring him to a x1 Base... or better. but protection via Communion only lasts a week until the next Sabbath. Maybe other Rites (Easter, Sacraments) should last longer...