SAFe vs Nexus

SAFe is not agile, it is just a marketing product for big companies.

I agree with Jose.  I am doing the Nexus cert next  because SAFE can get really quickly. It's difficult to understand and master. If you have a good grasp on the AGILE\Scrum Principles then I would go with NEXUS.

When I started scaling with Scrum I worked with a coach who wasn't certified in any specific framework, but he knew a lot of scaling patterns which really helped me get the concepts under my belt.  If you don't have access to a coach or a Scrum Master who has done it before and can offer guidance, I would start with the Nexus guide.  It is much more straight forward to learn, and there is a free guide here on this site under resources.  I am not totally anti SAFe, there are a few good patterns there that have been useful (e.g. WSJF), but overall it is not simple, highly prescriptive, and requires a lot of training across the organization.  Many won't have the appetite for that expense or training costs. 

There is also a nice book on Nexus written by folks from Scrum.org: https://www.amazon.com/Nexus-Framework-Scaling-Scrum-Continuously/dp/0134682661/ref=sr_1_1?ie=UTF8&qid=1529166748&sr=8-1&keywords=nexus+scrum 

You may also want to consider getting your Scrum house in order before scaling:

• Solid Engineering practices such as XP, and CI/CD tools (multiple Scrum Teams integrating code will be a challenge without it).  My first scaling effort had a lot of code integration challenges.
• Product Backlog: Multiple Scrum Teams sharing a Product Backlog - how will you manage dependencies?  Is your Product Owner ready for multiple teams?  How will work flow to the Scrum Teams?
• Are your Scrum Teams feature or component teams?  Feature teams will have less dependencies on other teams if they can deliver a feature that is vertically sliced through the technology stack.  Might there be an opportunity for the teams to self organize into feature teams if they are not already?
• How will you visualize the work?  How will you coordinate the work?  How will teams plan together, hold Sprint Retrospectives, etc.?  Will you have distributed teams?  Just a few things to think about.

All the best

Without even considering SAFe's pros or cons, I think it does itself and Scrum a disservice by using Scrum terminology but changing the definitions of those terms.  

Suppose there are two universities, One allowed all the students who pay a good amount of money and the other one allows only the candidates who deserve it.  

It shouldn't be an either or. If you're looking for work with large, global enterprises, you'll like see a SAFe certification as a prerequisite because of its popularity with leadership at these businesses. SAFe is very complex and leaders like it because it gives them a detailed implementation map.

For your personal growth, and if you're willing to invest in yourself, you should look into in-person certification training classes with all major Agile organizations granting certifications today. It will help you stand out.