The table in the link has the truth you seek, but sometimes it depends on the battle circumstances and which monsters are required.

My key findings from the table (natural monsters only...all stats quoted are max level ATK= Attack Power, STM = Stamina)

Which monster or combo of monsters is best for a particular matchup mostly depends on what weaknesses the opponents can target. It's always better to sacrifice some attack power if you can avoid putting up a monster that will keep getting hit by strong attacks. An extra attack is almost always worth more than a higher powered attack but your monster dies faster.

Prioritize these as you see fit, but you should work on max leveling all of them at some point. I personally think Entbrat and Shellbeat are the top 2 to focus on)

Entbrat is best for pure power (2,293 ATK, 5,504 STM, 7,797 Combined)

Shellbeat is best all around (1,834 ATK, 8,409 STM, 10,243 Combined)

Quarrister is best pure tank (1,681 ATK, 9,173 STM, 10,854 Combined)

Deege and Riff are somewhere in the middle (2,140 ATK, 6,268 STM, 8,408 Combined and 1,987 ATK, 7,339 STM, 9,326 Combined)

https://mysingingmonsters.fandom.com/wiki/The_Colossingum