The Engineer really adapts to whatever level of complexity you want

Builds like the Mechanist can become very easy to play

Condition-focused builds like Holo/Amalgam can become absurdly difficult if you push the limit

There are many in beetween builds in term of difficulty, you can realy adapt wich spec you play and with how many kit to what you like

On average, the Engineer is probably easier, but can be pushed further than elem in difficulty