Once you have Omega 9 at level 40 does it make sense to keep pushing its level up or to move to other bosses to level them up?
Yes, as it gets you the extra powers.
I would rather have all 4 before leveling them up. The original powers are best, except for seismic stomp, but that is that last for the amphibian.
I currently only have one boss, trying to get the second but its going to take a while. I foolishly spent most the dna i was getting for the trike, and used it on the rex to level it up. And i very much regret doing so 'cause right now i hardly use him. Seriously 30 - 50 bucks just to start a battle, and the prizes aren’t very good either. Anyway next time ill use the dna i get from the boss unlock rewards to unlock them.
Seismic stomp is the second power move Salamander gets and it is a fantastic move.
You can unlock the 2nd power at L40 just by pushing the Prestige button, it’s free and worth doing as you get Amber and the 2nd power. I chose to then level up the next boss before going on beyond L40, as I sometimes like to play the events where you use 3 bosses. All 4 of mine are now at L40, so I need to give the higher levels a try.