I would like to ask why people evolve their monsters into ultra form. For me it seems pretty bad idea to evolve it, because the only thing which changes is one new attack or passiv skill (not all of them) and the monster cost increases… So do the stats get better if ultraevolved or what is the advantage?
Yes, the stats get better. Also, after ultra evolving a monster, you might receive a necessary move. For example, if you ultra evolve gigarock (a legendary) into dragaia, then you get a move retreat. Retreat puts this monster, I believe, either to the back of the line, or next in the lineup. Hope this helped you! 
It puts it to the back, useful in Dragaia’s case because he can then make use of last bite too.
Stats get alot better too
Looks more badass as well
Stats increase by heaps
Plus they sometimes gain extra moves or better moves and passive abilities
The speed never increases though.
But the point is who should ultra evolve as their is only benifits
But the stats get better with the youth fruits, do they also increase a second time with the ultra evolution ?
thank you all:)
Yes they do
ill say that some monsters are necessary to ultra evolve, So far all the legendarys are worth the ultra evolve.
Epic/Super monsters with unwanted friends, Stun Bomb, Sleep Bomb and sacrifice summon are not necessary since you only gonna use them for 1 skill to support your team, but when you ultra evolve their stats get better which means they can survive a few hits before you can use them because from what I have those monsters have Low speed which means your opponent is more likely to kill them before you even use it which is why I recommend to never put these type of monsters in the starting 4 unless you have a Protector with Stealth teammate. Also epics with reckless attack and One on One like redgaroo are not worth the ultra evolve.
So ill say Legendarys, Assisted monsters, Protectors, Dual Killers, Healers, maybe Poison eaters/massacre and Timestrikers/Bloodcravers are the only monster you would want to ultra evolve.
This is all opinion btw
later you have enough cost points that there isnt really an issue with that unless you want to run 16 legendaries, which atm you cant even at max level.
Thanks:)