We stock both of the Scott's - but not the Serious so I'll try and be as unbiased as I can.
To be honest - I'd never heard of the Serious brand before this post, so I did a bit of digging on that bike. Shimano E-8000 for that sort of money is a good shout. I put the E-8000 on a par with the Bosch Performance CX, but it's all personal preference when it comes to either motor. Both are paired with a 500wh battery so no comparison there.
The Serious is running a + sized tyre whereas the E-Scale 710 is running a standard 27.5". Again, all personal preference neither one is better than the other.
Going onto the forks, the Serious is running a Suntour coil fork, whereas the E-Scales are both running Rockshox or Fox air forks which should prove to be more smoother and more reliable in the long run.
All are running shimano, both the 710 and Serious being 11 speed and the 720 being 10 speed. Would you notice the difference between 10 and 11? Most probably not, but if you're spending that sort of money you may want the best you can get.