What aspect of Customer Experience is more vital for growth and how?

Carlos,
Customers initially BUY based on perceived value ... usually represented by cost.  Customers STAY based on customer care (service) ... usually based on what they experience. 
These two concepts are not new news to anyone.
Strategy drives both of these concepts.  How much margin ... revenue minus expense ...must I have to be profitable? 
How much customer care can I afford (yes, care does cost the firm) vs using a self-care model or allowing the customer to suffer. 
Once these questions are answered then comes your process question.  How can the firm develop AND EXECUTE on the processes based on the strategic decisions of the leadership team. 
So to answer your question directly, there is no single aspect ...it’s a blend of your variables and others…
Hope this gets your questions started.

Resolve customer query/complaint to his satisfaction in shortest possible time, which means your processes are working, customer service is good, customer will recommend your product to others so sales is good, your brand improves as satisfied customer become your brand custodian, you improve your strategy as you are listening to end user

Hi Carlos,

I’ll try to make this as short as possible but also give some pointers:

First of all, I agree with Richard and Sajid. Therefore I’ll just add for what I found to be best practices.

TL;DR
- The whole picture
- Strategy
- Brand
- Usability
- Fulfillment
- Support

“Detailed”:

The whole picture:
If a competitor decides to offer your product for cheaper, why would customers remain with/choose you?

Strategy:
- Did you do your market and customer research BEFORE doing major hirings, investments or production?
- Will customers be willing to pay for it? (See the demise of Email/Calendar-App Startups)
- Do you re-test your Strategy, Brand and Value Proposition periodically to accommodate market changes and shifts in customer needs/expectations?
- Do you have a plan on:
a) how to advance your product/customer base, once your first mission is “achieved”?

Brand:
- Do your design, behavior, and language meet your customers’ standards?
- Does your presentation communicate clearly your Product/Service it does?

Usability/Fulfillment/Sales:

- Is the process from “Welcome” to “Sold” as concise as possible?
- While giving all the information to give the feeling of having made an informed decision to buy, not all should be “all there, at all times”. Present the essentials during your funnel and make supply the rest through in-line links on subpages. Basically, don’t overwhelm the customer.
- Instead of offering only a limited amount of payment options because you are dealing with it yourself, consider using payment providers. Don’t stop an already convinced customer at the last second from purchasing because you only accept credit cards or whichever time-consuming second payment method.
- Getting the sale is not the only primary objective. Yes, you want the sale but you also want the customer to enjoy the process and do it again, (as mentioned above) recommend your service/product to friends and don’t regret the whole thing and try to cancel/discontinue they purchase/subscription.

Support:
- Your support needs to be scalable (google the shitstorm N26 got in their early days for having Facebook chat their main means of reaching support and replies being slow)
FAQ/Knowledge Bases s or Helpdesks are great. But not all customers have time for that, have unique questions or just want a quick answer.
- If in line with your products brand, something Low-Fi as having a well-moderated Subreddit can be more efficient and cheaper to maintain then a dedicated Community forum.
- Avoid Email-Forms for support.
- If your business relies on sales/support agents on phones, unify their sources of information and datasets. Also to ensure the quality and efficiency of service consider supplying them with a tool like https://i2x.ai/
- Live Chats in combination with Knowledge Bases and Tutorials are a good solution. It allows for quick feedback and not relying on audio avoids problems due to support agent’s or customers dialect or phone connection.
- A great example for Support and Contact method is Squarespace. Knowledge Base, Helpdesk and their Live chat supports uploads of screenshots and sharing of “video how-to’s” by their agents

Since it’s not part of your question, aspects of internal company/team aspects are not mentioned here. After all “I’ll try to make this as short as possible” ;)