RE: Steem Monsters Question: Level Up or Try to Sell Extras?

I was maxing out by combining, but I've decided to combine up to level 9 and let them get the last few hundred XP in battle.
You can get roughly two level 9's or one level 10 for the same number of cards, so if they both battle a few hundred times to max out, you end up with two instead of one.
That's my strategy, although it assumes level 9 cards will be not much worse than level 10's.
We'll have to wait and see :)