I just started playing this game, and I'm wondering what differences there are in gameplay between the Holy and Unholy trees. Does either tree have powers that are unique in functionality to each tree and not just analogous to each other? Are there any powers that give you an advantage in gameplay?
The holy tree focuses mainly on Dante's Holy Cross attack, which is more of a ranged attack that damages foes at a distance. The Unholy tree focuses on Death's Scythe, which is a close range/combo weapon. If you have a preference for one weapon over another, that might inform your decision.
Some people find the Cross to be a bit button-mashy, and the Scythe to be a bit more 'skillful' but that's more personal preference than anything else.
The consensus surrounding skills is that Divine Armor (in the Holy skill tree) is among the most valuable skills. It can protect you and heal you at higher levels. The Unholy tree has many high-damage output attacks though.
You don't have to choose one path, although specializing early to get Divine Armor up to level 2 or 3 sounds like a winning strategy.