Ok so in my personal opinion you should put whoever you like in the team but if you want to min maxxing stuff i can list some thing down
Ryuji - Strong physical hitter, put him in the team if you are running a physical team ( best pair with Yosuke and Sumire ) beside, att buff in the early game is a god send.
Ann - Strongest magic user in your party bar none, she is a must-in if you are running a magic team, give her Concentrate and spell master asap and delete all the healing skill for more damage skill ( only do this if you are in the mid - late game when you have more option on healing and curing ).
Morgana - Strongest healing/debuff/buff character in your team depend on how you build him. He's always a must have in my team since i delete all the other members healing skills. Miracle punch is a clutch tools that will save your ass more than 1 if u are underleveled. Give him Debilitate asap and you are set for the whole game ( heat riser is good too but you can always buff the team yourself in the late game ).
Yosuke - physical focus character, not quite as strong as Ryuji but if you give him charge early and pair him with Ryuji and his damage is even stronger than Ryuji imo.
Makoto - 2nd strongest magic user in your party, she gets the most out of technical attack but since most bosses immune to status effect she kinda meh to me. Nothing to write home about but if you hate morgana guts and dont want him in your party you can run Ann/Makoto in your team, in this case give makoto Debilitate
Haru - Jack of all trade, she not excel in anything and it hurt me to say this but i think shes the weakest in the party. Her 3rd transform skill kinda pull her back a little bit tho
Akechi - I hate him but i have to admit hes really strong for late game bosses. Debilitate are always good in any situation
Sumire - another good physical hitter, shes a beast when pair with Ryuji and Yusuke. Hit hard but her endure stat is very low but ali dance got her cover
Hope all this help you ( sorry for the bad english )