Personally I'd like to use them both along Crono but I think not many people do.

Both Marle and Frog have Water elemental attacks and healing magic that are quite useful.

Which of these two do you usually prefer? Marle is more supportive and Frog is more offensive.

Frog's Cure isn't all that good, what was it? FrogLick? So I just used Marle, her Cure Spells did a lot more.

Frog also has Heal which mediumly heals entire party and also has Cure2 which heals one's HP almost upto max. I used him and Marle all the time they can have some good curing combination skills together.

I use them both in my party. Especially useful against Lavos becuase you can use double cure which heals 999. So personally i say both.

I agree about preferring attackers than mages. In Chrono Trigger really key part of the fighting is to coordinate timing of three different characters so that they can use combination as soon as possible if wanted to, without wasting time of waiting till another's gauge fills up. If you are using fighter, you are likely to be not scrolling down your tech options all the time, so it is easier to have smoother fight.

I liked using Frog more. He's strong and he's just plain cool. In important battles though I'd probably take him out for Marle since she's more useful as a healer.

I usually have Frog, as his heal attack heals everyone Its real handy!

I agree that Frog has high compatibility with Crono. Actually, Crono has high compatibility with Marle as well. That's the main reason why I use Crono, Frog and Marle in the game.

Crono and Frog combination yields powerful attack while Marle can heal. Crono can damage and Marle and Frog can heal in really severe situation. Crono and Marle can do some Ice Sword damage (they are pretty strong if u havent really noticed. It is really basic attack but its absolutely worth the MP points used) and Frog can do Heal if everyone needs moderate healing.

Yeah, spire is really strong and frog has a plus: HE has an attack that heals the entire party.

I use Chrono Frog and Ayla that always gets the job done I nearly never use Marle she is my least favourite character and is also one of the weakest the only time she is have decent is when in boss battles where healings is necasary often

Nah Marle's not that weak. I use both Marle and Frog now. The Arc Impule triple tech is devastating. And when she uses Double Cure with Frog, it can heal everyone practically full.