Which is better for investment Nirala Aspire or the Gaur City Project in Noida extension?

They are both likely to appreciate in the same way given the location and fact that both projects are still under construction. 

They both however focus on different things. Gaur is all about making life more convenient by having amenities like schools, banks, hospitals etc. within walking distance. Whereas Nirala focuses on improving the quality of life by having fewer amenities and more open space, about 80% of the project is open space. 

You need to look at what is more important for you and your family, based on that I would say take a call. Also, While Gaur has only 2&3 BHK apartments, Nirala Aspire has 2,3 and 4BHK options, and more layouts and options.