I have had both,and whatever you get having a longer shaft length aids in stowing.Lessens the crouching to grab control head to stow.
Xi5 remote is lightweight and floats,but if you are hard of hearing you may not hear the tones when setting-up/calibrating.Everything on MK remote is visual,no need to listen for musical tones.Xi5 foot pedal is something you have to get used to,it steers much faster than MK models.That pedal really needs a power on/off indicator,lot of guys leave it on and battery life is shorter.
Customer service,Minnkota is far better than MotorGuide.My Xi5 was pretty much a lemon until I replaced the Pinpoint module,the older ones are flaky and they know it.I wanted them to send a new one(sent photos of old one with broken wires),and they told me to send to ASC which I did not want risk of it being destroyed in shipping.
In all,I think you will be happier with the Terrova.