There's a thought that having more cards on the battlefield leads to better outcomes. And there's some truth to that. For one, you get the summoner boost for more cards. That has a multiplier effect as you get more attacks and your opponent has to take out more cards. But sometimes, it can be better to have fewer, but stronger cards.
Here's a battle that shows the difference. My opponent had 6 cards while I had only 4. Then, my opponent also had quite a big summoner boost with 4 cards getting a boost while only 2 of mine got one. So at first glance, it isn't looking good for me.
But by the middle of round 2, it had evened itself out. Still, my opponent had a decent attack advantage.
And then it comes down to the final two. It was going to be a slug-fest and that's where having a proper tank like the Imperial Knight made a big difference because of its healing ability.
Eventually, I won the battle even though at the start, I think most would have been doubtful looking at the lineups. You can catch a replay of the battle here: https://splinterlands.com/battle/sl_f8342515563b7a1ecc23b192de8cc682?ref=charcoalbuffet
It's the age old debate because there are mana constraints - quantity or quality. My personal preference is to choose as many heavy hitters / tanks as I can. The only exception is if the summoner boost is able to make an outsized gain. That was the case with Alric but since playing in Modern, I have switched to fewer but stronger cards.
