Is there a difference between juices extracted using a juicer and a blender?

No, there is no big difference that you should worry about. 

The most ideal is to juice in a slow-pressed juicer, as it does not produce heat, thus preserving more nutrition. 

However, if you're using a blender, it is completely okay. 

Start with what you currently have access to. Later, you may invest in a good, slow pressed juicer if you wish.