This is a long-standing question and the simple answer is no, while the longer one takes a little bit more to explain. Spinning vs cycling is a theme which many have tried to answer, albeit the real answer lies in you. If you want to go outside or like going outside, cycling is better even though indoor cycling has its own benefits.
Here are some things to consider when choosing which of the two you are going to commit your time to.
The Level of Intensity – Hardcore Workouts
To make things clear, both spinning and cycling can make for hardcore workouts. The difference is that one is performed indoors on a stationary bicycle which can get boring really fast. The other difference is that a stationary bicycle is just that, stationary. It engages certain muscles in the body but neglects others which would be active while cycling.
These muscles are called stabilizers and they have the function of stabilizing your body movements so that you do not fall. They are extremely active while you cycle, especially if you stand while cycling. Your bicycle tends to move side to side, following the natural force of you stepping on the pedals. This can make an intense workout even more intense.
Spinning is stationary and it activates less muscles, though you can easily change the level of intensity on the machine or turn up your cadence. The thing you would be lacking is incline, however, and natural wind resistance which makes things harder, always.
You could easily burn up to 600 calories on a stationary bicycle while you could burn up to a 1000 calories outdoor. These figures are achievable if you really hit the pedals hard.
Safety and Convenience
Indoor bicycles are safer and that is a fact. Outdoor you may run into potholes, traffic, bad weather, animals, other cyclists and a plethora of other hazards. Going to work on a bicycle is convenient but if you work at home, then sitting on a stationary bike while working is a great workout.
The fact is that both are great ways of exercising and neither is really better. The question which one will help you exercise more efficiently and whether you like going outside and climbing hills or pedaling with your favorite music and TV show on. That question, however, only you can answer.