How To Use the Rowing Machine (IT DOESN'T GET ANY EASIER THAN THIS) P.S. I like the Concept 2 machine!
https://youtu.be/IsJdW9NztEI
They work different muscles with different intensity. Rowers work the arms and shoulders primarily. Ellipticals work arms to some extent and mostly work the thighs and the rest of your legs. Ellipticals are very good at building muscle if you can handle high resistance -- the setting is up to you. They are mostly cardio if you work at low resistance and move quickly; they are mostly resistance training if you put the resistance up very high in which case you will have to go much more slowly. In other words, these machines are not comparable -- they focus on very different exercises both of which are quite good but the intensity of which depends on how long you do it for and how much resistance you use. And don't forget to consider which exercise seems fun to you. But varied routines are best both for building overall body tone but also for preventing boredom and plateaus, so owning both machines would actually be the best answer to your question. But if you go to a gym, they have both machines, plus a host of other things to do -- you'll never replicate what you can do at a gym with what you can do at home unless you're quite wealthy and can build your own gym.
You will get a better workout from a rower! It's not difficult to learn the proper technique. Your not going to get ripped either. to really build muscle you need to do strength training.
Try either going to a gym and ask about learning the technique. google classes in your area that teach rowing.