I just caught a Ponyta, which is 1 of my fav Pokemon.Should I keep it in my party? Which 1 should be replaced?

I just caught a Ponyta on Pokemon Diamond, and I'd like to add it to my party but I'm not sure which one to replace it with.

At this point of the game, I just beat Gardenia and am heading to Route 211.

Here is my current party:

Psyduck - Level 18

Staravia - Level 20

Geodude - Level 17

Prinplup - Level 18

Budew - Level 18

Luxio - Level 16



I'm thinking Luxio would be the best to take out of my party (Even though I am quite fond of it).



Which one would be the best to take out to replace with Ponyta? Why?



Thanks :)
I just caught a Ponyta, which is 1 of my fav Pokemon.Should I keep it in my party? Which 1 should be replaced?
Take your Luxio out, especially if Ponyta is way stronger than Luxio. Or if you're extremely fond of your Luxio, put Ponyta in place of Psyduck since you already have a water Pokemon in your party. Just be sure to train your Luxio until its level has caught up with all your other Pokemon.
Reply:I also think Luxio should be taken out of your team.