If you level faith to around 24, you'll have some great support/heal miracles in your arsenal. Level it to 30 for strong offensive miracles (provided from a certain covenant and an elusive npc).
If you level Intelligence to around 16, you'll have even more support spells to choose from, although, many of these spells are hidden and require an extra degree of exploration.
On the flip-side, leveling Int beyond 30 will yield very strong sorcery much later in the game that will put away most enemies (PvE) easily from a distance, and just enough faith (14-16) for a few healing/offensive miracles.
With enough attunement slots and a trusty bow/cross bow, you could potentially ditch your melee weapon/shield in favor of an arsenal of magic while having strong armor equipped that's still light enough for you to fast-roll.
You can still find very strong weapons when going through the faith/int route, but you'll have to find and craft specific weapons that increase in strength when you level int and faith.
All of this might make more sense the more you become familiar with the game.