You know I enjoy riding the bike and I think it is the best piece of equipment to strengthen and tone the legs. If you go to the gym and have to decide between the upright and recumbent, is there a difference and which one is better?
I like the upright because you are in the more natural riding position and since I ride outside, I want to be in that position to train. If you are new to the bike it may be better to start on the recumbent because you will be in a more comfortable position. Also, if you have low back issues, again, the recumbent is for you since you have the back support.
Ultimately, when you are looking for where you can get the best workout, both pieces are going to give you the cardio workout you want and get the legs strengthened!