When choosing a new piece of exercise equipment for your home, you may have been looking at both Electrical, or Mains Powered Cross Trainers and Manual alternatives.
To explain, there really are only two simple differences. The ability to program the machine and use automatic programs, and how smooth the resistance change will be.
Mains driven machines are their powered from a standard mains socket, which means the computer can be much more flexible and dynamic. There will be a motor inside the flywheel cover which takes instruction from the computer, and automatically changes the resistance level. So, you will usually be able to choose an automatic program that will replicate undulating terrain, and increase and reduce the resistance as if you were going up and down hills and alike.
As the resistance change is electrical, the change is smoother than a manual machine. A simple analogy would be to compare an automatic car to a manual gearbox alternative.
The manual elliptical require usually a dial turn to alter resistance, so automatic computer programs are not possible.
So, which type of elliptical cross trainer is best? Well, of course you need to compare build specification, size, quality etc. Generally mains powered machines are of higher build spec, but not always. But in respect of the manual v electronic versions, then if you are experience and looking for some more dynamic training you may want the option of the extra programmability. If you are more of a novice, and wish to set a resistance levels then simply work away, then there is no reason why a manual machine, which is usually cheaper, would not suite your needs sufficiently.
So, the choice is yours!