I usually run Crono Maus Ayla.
Crono with Prisim Specs, Magus with Gold Stud and Ayla switching between Sun/Prisim Specs, Gold/Silver Stud, or Charm Top depending on which play through I am on and what I am doing.

Strengths:
- Everyone has an extremely powerful damage tach
- You can charm all the good stuff off every boss
- Magus's low level Magic can AoE through most fights when you combin his high magic stat, the fact that his level 2 elemental spells are over a third more powerful to begin with, and his ability to match all elemental weaknesses.
- Between Chrono and Ayla you have the ability to deal a ton of Physical damage through techs or attacks.

Weaknesses:
- Healing. I usually save up all my Magic Tabs from the game and give them to Ayla, doubling her naturally low magic stat and causing Kiss to heal for over 600 damage. Lack of AoE heal still hurts though.
- Weak in the double tech department. Falcon Hit is super useful in situations, but I never use any of the others.
- Magus is quite weak against Zeal, but I take him anyways for the music.

I've beaten the game without Magus or Crono, but I always pick them up unless I have a reason not to.